What to do when a PDF won't open

First, rule out the boring causes

Before assuming corruption, check three things that look identical from the outside:

• An incomplete download. Compare the file size with the source: a 2 KB “PDF” is an interrupted transfer, and no repair tool can invent the missing part. Download it again.
• A file that isn't a PDF. Some downloads arrive as an HTML error page saved with a .pdf name. Opened in a text editor, it shows a web page instead of the characters %PDF at the very start.
• A password. If the reader asks for one rather than showing an error, the file is fine.

Try a different reader

Browsers are more forgiving than desktop readers. Drag the file into a new tab, or open it with “PDF reader”.

If it displays there, the document is readable and the problem is your application. Printing the page to PDF from the browser then gives you a clean copy.

Rebuild the file in 3 steps

1. Open “Repair PDF” and select the damaged file.
2. The tool walks the document object by object, finds the page content that survived and builds a valid file around it.
3. Download the repaired version and check the pages that matter before sending it on.

Everything happens in your browser: a damaged contract or medical record never leaves your device, whereas “send us your broken file” is exactly what you'd rather avoid with that kind of document.

If nothing opens it

There is often text worth saving, even without the layout. “PDF to text” extracts whatever is readable, which is usually enough to rebuild the document rather than lose the work. If it was a scan, run the repaired version through “OCR” to get selectable text back.

To avoid a repeat: let downloads finish, don't close an application mid-save, and avoid editing a PDF directly on a USB stick or a flaky network drive — copy it locally first.