How to use the PDF viewer
- Drag a .pdf file onto the drop zone, or open it with Choose files.
- Pages appear one after another on a gray workspace. Click a thumbnail on the left to jump to a page, or use the arrows in the status bar.
- Use the zoom buttons in the status bar to zoom between 25% and 400%, and the fit button to fit the page width again.
- Copy all text collects the text layer of every page in order and puts it on your clipboard.
- Fullscreen fills the screen for reading, and Print / Save as PDF prints right away.
Rendering with Mozilla PDF.js
The viewer uses PDF.js (Apache-2.0), the same PDF engine built into Firefox. A PDF is a set of drawing instructions that say where to place each character, line and image on a page. PDF.js interprets these instructions and paints them on an HTML canvas.
- Web Worker processing: the heavy work runs in a background thread, so the page does not freeze when you open a large PDF.
- Lazy rendering: pages are drawn only when they come near the screen, so even documents with hundreds of pages open quickly.
- High-resolution displays: pages are drawn at your screen's pixel density, so text stays sharp on Retina and other high-resolution displays.
Why text cannot be copied from scanned PDFs
A PDF created by scanning paper or photographing it with a phone looks like text but is actually an image. It has no text layer, so copying returns nothing. Such documents need OCR (optical character recognition) first. The related guide explains free ways to run OCR on your own device.
How is this different from the browser's built-in PDF viewer?
Chrome and Edge have PDF viewers too, but you usually have to download the file first, and mobile browsers often hand PDFs to another app instead of showing them. This page shows PDFs the same way on every device, and lets you open HWP, DOCX and Excel files in the same place, in tabs or side by side.
Password-protected PDFs
PDFs that require a password to open are not currently supported and show an error message. Ask the author for an unlocked copy, or open it in a PDF program that asks for the password. Because everything runs locally, no record of which PDF you opened is kept anywhere.
Frequently asked questions
Is there a PDF size limit?
There is no server limit because nothing is uploaded. Documents with hundreds of pages open fine because pages are drawn only when needed.
Why can't I copy text from some PDFs?
PDFs made by scanning paper contain images, not text. Run OCR on them first and try again.
Can I edit the PDF?
This tool is for viewing, printing and copying text. Use a PDF editor if you need to change the document.
Does zoom work on mobile?
Yes. Use the zoom buttons in the status bar, and scroll the page with your finger to see the part you need.