Comparison
This page puts C-A-R-T-A next to the most widely used PDF readers: how big they are, how much memory they ask for, what they cost, whether your files stay on your device and what they can do. Where a figure is not available in an official or reliable source, it says "not stated" or "?": nothing is made up.
Date of the comparison: 1 November 2026. Competitors' pages change often (new versions, new plans): before deciding, check the source given. This comparison is written by the author of C-A-R-T-A, so read it with that in mind: that is why every number has its source, and C-A-R-T-A's own measurements are described below so you can repeat them.
The short version
- Size. C-A-R-T-A is not installed: the first visit downloads about 5.1 MB (about 1.9 MB over the wire, compressed), and after that it works without a network. Programs you install range from about 10 MB (SumatraPDF) to over 400 MB (PDF-XChange Editor, a third-party Foxit package) and ask for hundreds of MB of disk.
- Memory. In a test with one tab and a one-page PDF, the browser processes devoted to C-A-R-T-A used about 150-250 MB, of which the JavaScript heap is only 3-5 MB. A photographed scan rises to about 500 MB. The browser has other processes too: the real numbers are in the measurements section.
- Features. C-A-R-T-A covers a lot: signed files, Italian e-invoices, OCR, page organising, compressing, blacking out, comparing, measuring, stamps, AI. It does not do everything: it does not edit the text of a PDF, it does not convert to Word or Excel and it does not produce qualified digital signatures. See "Where the others are stronger".
- Files. They stay on your device, except when you press an AI function or the "On the server" OCR. Web services (Smallpdf, iLovePDF) send the file to a server instead and say they delete it after 1-2 hours.
Size, memory, price, files and AI
Sizes are in megabytes (MB, one million bytes), except where MiB is written. "Not stated" means the official page does not give the figure. Figures from unofficial sources are marked as such.
| Reader | Platforms | Program size | Memory and disk required | Price | Where the files are | AI |
|---|---|---|---|---|---|---|
| C-A-R-T-A | Any modern browser (computer, phone, tablet); installable as an app | First visit about 5.1 MB (about 1.9 MB compressed). On-device OCR: about 5.8 MB more, once | No requirement stated. Measured: see below (JS heap 3-5 MB; tab processes 150-500 MB depending on the document) | Free, no account | On your device. They go to the compiler (a private server) only if you press an AI function or the "On the server" OCR | Yes, on the compiler (Claude), only on request |
| Adobe Acrobat Reader | Windows 64 and 32 bit, macOS; mobile app | Not stated. Mobile app: not found | 2 GB RAM. Disk: 900 MB (Windows 64 bit, English), 1 GB (other languages), 4.5 GB (Windows 32 bit), 380 MB (macOS) | Free; editing text and images needs an Acrobat subscription | Not stated in the pages read | AI Assistant: limited requests free, full with a paid add-on. Where it runs: not stated |
| Foxit PDF Reader | Windows 10 and 11, macOS 10.15-14, iOS, Android, web | Not stated by the vendor. A third-party (unofficial) deployment package of 2026.1.1 is about 394 MB | 512 MB RAM (1 GB recommended) and 1 GB disk, per the official version 10.1 manual (dated) | Free | Not stated; integrations with cloud services (SharePoint, DocuSign) | ChatGPT integration (details not stated) |
| PDF-XChange Editor (free version) | Windows (also ARM64) | Version 11.1.1.0: EXE installer 430.4 MB; 64-bit MSI 383.6 MB; portable 154.5 MB (99.0 MB without OCR) | Not stated (the official page lists only operating systems) | Free for about 70% of the features; the rest needs a "Plus" licence | Not stated; opens files from Box, Dropbox, Google Drive, OneDrive, SharePoint | AI assistant: your data is not processed by AI models unless you supply your own API key |
| SumatraPDF | Windows 7-11 (64 bit, 32 bit, ARM64) | Version 3.6.1: 64-bit installer 10.56 MB; portable 9.57 MB | Not stated | Free | Not stated | None mentioned |
| Okular (KDE) | Linux, Windows (Microsoft Store), macOS (test builds) | Not stated for Windows. On Linux (Flathub) about 34 MiB to download and about 82 MiB installed | Not stated | Free (free software, GPL 2 or later) | Not stated | None mentioned |
| PDFgear | Windows 10 and 11, Mac, iPhone/iPad, Android, web tools | Not stated by the vendor. Third-party sites report about 93 to about 135 MB, depending on the version | 512 MB RAM (1 GB recommended) and about 500 MB disk | Free, "without signing up" (the site's claim) | On the computer; chatting with the PDF needs internet | Yes (chat and summary with the PDF), online; model not stated |
| Xodo | iPhone/iPad, Android; Windows and browser in the Pro version | Android app 10.15.0: 81.18 MB (third-party listing, APKMirror) | Not stated | Free with in-app purchases (converter $11.99 one-off; Mobile and Pro subscriptions $107.99 a year) | Not stated | Not found |
| Chrome (built-in viewer) | Wherever Chrome runs | None: part of the browser | Not stated for the viewer alone | Free | On your device; OCR of scans runs on the device | None mentioned in the help pages read |
| Edge (built-in viewer) | Wherever Edge runs | None: part of the browser | Not stated for the viewer alone | Free | On your device (not stated otherwise) | None mentioned in the pages read |
| Firefox (PDF.js viewer) | Wherever Firefox runs | None: part of the browser | Not stated for the viewer alone | Free | On your device | None mentioned |
| Preview (Mac) and Files (iPad) | macOS, iPadOS | None: part of the system | Not stated | Free, included with the device | On your device | None mentioned in the pages read |
| Smallpdf | Web; desktop and mobile apps only with the Premium plan | None for the web version | Not applicable (runs in the browser; the server does the work) | Free with limits; Premium 5 € a month billed yearly (60 € a year) or 9 € a month | On a server: the file is uploaded; the site says it is deleted after one hour of processing | Assistant, summary, translation: in the Premium plan (2,000 AI credits); online |
| iLovePDF | Web; desktop and mobile apps only paid | None for the web version | Not applicable (runs in the browser; the server does the work) | Free with limits (for example files up to 15 MB for OCR, 100 MB for the other tools); Premium plan (price not read) | On a server: the site says files are deleted within 2 hours of upload | AI summary; AI credits only paid |
Sources of the numbers
All pages were read on 1 November 2026.
- Adobe Acrobat Reader: system requirements; features and AI and AI Assistant.
- Foxit PDF Reader: product page; requirements from the official 10.1 manual (dated); size of the third-party package from the Tranquil IT WAPT catalogue, unofficial.
- PDF-XChange Editor: product page (sizes of 11.1.1.0, free part, AI) and system requirements.
- SumatraPDF: download and version history.
- Okular: website and install page; Linux sizes from Flathub.
- PDFgear: website and Windows guide; third-party sizes come from download listings (Softpedia, PCMacStore), not from the vendor.
- Xodo: App Store listing (prices) and the third-party listing APKMirror (Android app size).
- Chrome: manage PDFs in Chrome. Edge: PDF reader in Edge. Firefox: view and edit PDF files.
- Apple: fill out and sign in Preview and annotate.
- Smallpdf: home, pricing and security. iLovePDF: home, pricing and how to delete files. File deletion is a statement by the companies, not verified by independent sources.
C-A-R-T-A, actually measured
The C-A-R-T-A figures are not copied: they are measured on today's version, with the program served locally and a Chromium driven by Playwright. They can be repeated.
Size
The files were added up the program stores on the first visit (the "CORE" list of the service worker, which is what lets it work offline afterwards). Figures in megabytes (one million bytes), measured on the files on disk.
| Part | Size | What it holds |
|---|---|---|
| C-A-R-T-A's own code | 1.10 MB | 44 files: the page, the JavaScript modules, the style, the languages, the icons |
| Heading font | 0.03 MB | A single font file |
| PDF.js (reading PDFs) | 3.46 MB | Mozilla's engine, plus the scan decoders (0.47 MB) and the 14 standard fonts (0.80 MB) |
| pdf-lib (writing PDFs) | 0.52 MB | Annotations, pages, form filling, drawn signature |
| Total on the first visit | 5.11 MB | 68 files. Over the wire, gzip-compressed, about 1.9 MB (an estimate; it depends on the server) |
| Tesseract (on-device OCR) | 5.80 MB | The program (0.20 MB), the engine (3.94 MB) and Italian (1.66 MB). Downloaded only the first time it is needed and kept in the browser's storage |
The dictionaries for East Asian fonts (1.17 MB) and the colour profiles are not part of the first visit: they arrive only if a PDF uses them.
Memory
C-A-R-T-A was opened in Chromium (the same family as Chrome and Edge) with a single tab, then two of the site's sample PDFs: the supply contract (text, one page) and the phone scan (a photographed page, the sample with OCR). Two things were read:
- The page's JavaScript heap (a Chromium measurement, after a memory clean-up): about 3 MB at rest, about 5 MB with the contract and about 5 MB with the scan. This is the memory used by C-A-R-T-A's code.
- The processes' memory as Windows assigns it to the browser (working set): the rendering processes, which host the tab and its background workers, were about 150 MB at rest, about 220 MB with the contract and about 500 MB with the photographed scan, which has to be decoded and drawn at large size. Adding the browser's main, graphics and network processes, the total was about 270, 350 and 650 MB.
How to read these numbers: the memory belongs mostly to the browser and to the engine that draws the pages, not to C-A-R-T-A's code; with more tabs and long PDFs it grows. It is a single run, on a Windows server, with a browser without a window: rounded values that can differ on your device. The peak during OCR was not measured (it succeeded, but once finished the rendering memory had dropped to about 470 MB). The comparison with the other readers is therefore one of order of magnitude: competitors state minimum requirements, here actual use is measured, and the two are not the same thing.
Features compared
yes = the feature appears in the official pages; no = the pages say it is not there; paid = only in a paid plan; partial = available with limits; ? = not found in the pages consulted (it may exist: it could not be confirmed). For web services, "yes" means the tool exists; the free plan's limits are in the table above. On a phone the table scrolls sideways: the first column stays put.
| Feature | C-A-R-T-A | Acrobat Reader | Foxit Reader | PDF-XChange (free) | SumatraPDF | Okular | PDFgear | Xodo | Chrome | Edge | Firefox | Apple Preview / Files | Smallpdf (web) | iLovePDF (web) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Open PDFs | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes | yes |
| Signed .p7m files | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Digital signature verification (CAdES, PAdES) | yes | ? | yes | ? | ? | yes | ? | ? | ? | ? | ? | ? | ? | ? |
| Italian e-invoices (XML) | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Fill in forms | yes | yes | yes | ? | yes | ? | ? | yes | yes | yes | yes | yes | yes | yes |
| Auto-fill with your own data | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | yes | ? | ? |
| OCR (read scans) | yes | ? | ? | partial | partial | ? | ? | ? | yes | ? | ? | ? | yes | yes |
| Drawn signature | yes | yes | yes | yes | ? | ? | ? | yes | yes | yes | yes | yes | yes | yes |
| Annotate and highlight | yes | yes | ? | ? | yes | yes | ? | yes | yes | yes | yes | yes | yes | ? |
| Organise pages (merge, split, reorder) | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | yes | ? | yes | yes |
| Compress | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | yes | yes |
| Black out data | yes | ? | ? | ? | ? | ? | ? | paid | ? | ? | ? | ? | yes | yes |
| Compare two versions | yes | ? | ? | paid | ? | ? | ? | ? | ? | ? | ? | ? | ? | yes |
| Measure on floor plans | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Stamps, watermark, page numbers | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | yes | yes |
| AI summary or questions to the document | yes | partial | ? | partial | ? | ? | yes | ? | ? | ? | ? | ? | paid | paid |
| Deadlines into the calendar | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Check citations of laws | yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Read aloud | yes | ? | ? | ? | ? | ? | ? | ? | ? | yes | ? | ? | ? | ? |
| Several documents in tabs | yes | ? | ? | ? | ? | ? | ? | ? | yes | yes | yes | ? | ? | ? |
| Works offline | yes | yes | yes | yes | yes | yes | yes | ? | yes | yes | yes | yes | no | no |
| Installable app | yes | yes | yes | yes | yes | yes | yes | yes | no | no | no | no | paid | paid |
| Works without an account | yes | ? | ? | ? | ? | ? | yes | ? | yes | yes | yes | yes | ? | ? |
| Files stay on your device | yes | ? | ? | ? | yes | yes | ? | ? | yes | yes | yes | yes | no | no |
| Free | yes | partial | yes | partial | yes | yes | yes | partial | yes | yes | yes | yes | partial | partial |
| Open source | yes | ? | ? | ? | ? | yes | ? | ? | ? | ? | ? | ? | ? | ? |
The "?" are question marks, not "no": for the rows that are C-A-R-T-A specialities (.p7m files, XML invoices, law-citation checking, deadlines in the calendar) no matching feature appears in the competitors' pages, but that does not prove it does not exist in other forms, for example as an add-on.
Where the others are stronger
- Editing the text of the PDF. Changing a paragraph or an image inside the file: Acrobat offers it with a subscription (the free Reader does not, Adobe says so), PDF-XChange and Foxit have dedicated editors. C-A-R-T-A annotates, fills in, stamps, blacks out and reorders pages, but does not rewrite a document's text.
- Converting to Word, Excel or other formats. Smallpdf, iLovePDF, Xodo and Acrobat do it. C-A-R-T-A exports Italian e-invoices to Excel and makes searchable PDFs, but does not convert any PDF into Word.
- Outgoing digital signatures. C-A-R-T-A reads and verifies digital signatures, but its own signature is drawn: it does not carry the value of a digital or qualified signature. Signing with a certificate needs other programs: SumatraPDF and Okular, for example, say they can sign with a certificate.
- Maturity, support and guarantees. Acrobat, Foxit and PDF-XChange have years of history, support, manuals and business deployment. C-A-R-T-A is a personal project: reports go through GitHub, with no guaranteed support.
- Native apps and integrations. The competitors' phone and computer apps fit the system better (printing, scanner, folders), and some connect to cloud services. C-A-R-T-A is an installable web page: on iPad and iPhone it has the browser's limits, described on the devices page.
- Features C-A-R-T-A lacks. For example creating fillable forms from scratch (PDF-XChange Plus, iLovePDF) and the features of a full suite.
Where C-A-R-T-A is different
- It opens in a page, with nothing to install and no account. The program is about 5 MB; programs you install weigh from about twice that (SumatraPDF, 10 MB) to over a hundred times (PDF-XChange Editor, 430 MB), where the figure is stated.
- Files stay on your device by default. What leaves is your decision, by pressing an AI function or the "On the server" OCR. The privacy text explains what is sent and where.
- Built for Italian office documents. It opens signed files (.p7m and similar), verifies CAdES and PAdES signatures, shows e-invoices in readable form, checks citations of laws and rulings, puts deadlines in the calendar, fills in forms with your data.
- Free where it counts. The functions that run on the device are free and need no sign-up; only the AI functions depend on the organisation's compiler.
- Open source. You can read it on GitHub, in the "pdf" folder.
How to read this comparison
This page is not meant as marketing: every figure is attributed, and where a source is missing the table says "not stated". If you find a wrong or outdated number, report it from the questions page: it will be corrected and the date updated. For the full list of what C-A-R-T-A can do, go to the features.