Edit a PDF without uploading it
Every file you drag into a typical online PDF editor is copied to someone else's computer. PdfCanvas does the work inside your browser tab, so the document never travels.
What happens when you upload a PDF
A server-based editor sends your file over the network, writes it to disk, processes it, and returns a new file. That round trip is invisible, but it creates at least one copy on hardware you do not control. Retention rules vary, and the privacy policy decides how long the copy stays.
For a receipt or a school worksheet this may be acceptable. For a contract, a payslip, a medical letter or an ID document, it is a real decision with legal weight under GDPR.
How local editing works instead
PdfCanvas reads the PDF with PDF.js, edits existing text with a WebAssembly build of PDFium, and writes the result with pdf-lib. All three run in the tab. There is no API call, no queue, and no upload endpoint to trust.
You can verify it yourself: open the editor, load a document, and watch the network panel in your browser dev tools. The only requests are the static files needed to run the app.
PdfCanvas vs a typical online editor
| Feature | PdfCanvas | Typical online editor |
|---|---|---|
| File leaves your device | No | Yes |
| Account required | No | Often |
| Watermark on free tier | Never | Sometimes |
| Source code available | Yes, MIT | No |
| Works after disconnecting | Yes, once loaded | No |
What to check before trusting any PDF tool
- Does the tool describe an upload, or does it say processing is local?
- Can you inspect the network requests and see whether the file is sent?
- Is the client code open source, so the claim can be verified rather than believed?
- Does the free tier add a watermark or a page limit?
- Can the tool keep working when the connection drops?
Frequently asked questions
+Is a browser editor slower than a server one?
For normal documents, no. Rendering and export take a second or two. Server editors add upload and download time on top of the same work.
+Can PdfCanvas see my file at all?
No. There is no backend that receives documents. The site is static files and the editor runs on your machine.
+Does it work with large PDFs?
Yes, up to 200 MB by default. Memory is the real limit, and very large scanned files are slower to render.
+What if I close the tab?
The open document is gone unless autosave is active. The hosted editor keeps a local copy in IndexedDB so you can reopen it in the same browser.