Why PDFs Get Corrupted
PDF corruption most commonly happens during file transfer: an interrupted download, a network drop while attaching to email, or a USB drive removed before the write finished. It can also happen when multiple applications save to the same file simultaneously, or when an old application writes a PDF that doesn't fully comply with the spec. The result is usually a malformed cross-reference table — the index that tells PDF readers where each object starts in the file.
Signs of a Corrupt PDF
Common symptoms include: Adobe Reader shows 'This file is damaged and could not be repaired', the file opens but pages are blank or show garbled characters, the file opens in one viewer but not another, or the page count is wrong (showing 0 or 1 page when you know it's longer).
- Try opening in multiple viewers first — Chrome, Firefox, and Preview often handle slightly malformed PDFs that Acrobat rejects
- Check if the file size seems right — a 50-page report shouldn't be 2 KB
- Try to re-download the file from the source before attempting repair
How PDF Repair Works
Our repair tool re-parses the file using pdf-lib, which attempts to reconstruct the cross-reference table from scratch by scanning the file for valid PDF objects. This recovers most cases where the corruption is in the metadata structure rather than the actual content stream. If the content itself (image data, font streams) is corrupted, recovery may be partial.
Step-by-Step: Repair a PDF in Your Browser
1. Open the Repair PDF tool and upload the damaged file. 2. Click Repair — the tool will attempt to re-serialise the PDF. 3. If successful, a download button will appear with the repaired file. 4. Open the repaired file to verify all pages and content are intact.