Repair PDF
Fix PDFs that won't open, show errors, or are bloated — repaired privately in your browser.
Drop the damaged PDF hereChoose a file to get started
Repair starts automatically. Your original file is never changed.
Processed in your browser — files never leave your device
How to Repair a Corrupted PDF
Few things are as frustrating as a PDF that refuses to open — especially when it's an invoice, a signed contract, or the only copy of a report. Messages like "the file is damaged and could not be repaired" or "failed to load PDF document" usually don't mean the content is gone. More often, the internal index that tells a reader where each page lives has been broken by an interrupted download or a crashed save. PDFDoco's Repair PDF tool rebuilds that structure automatically, right in your browser, and verifies the result before you download it.
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Upload the damaged PDF
Drop in the file that won't open, shows errors, or is suspiciously large.
- 2
Automatic diagnosis
We check the header, cross-reference table, and file ending for common damage.
- 3
Structural rebuild
Every recoverable object is read and the document is rewritten cleanly.
- 4
Verified download
The repaired file is test-opened before download, so you know it works.
Two-stage recovery
A lossless structural rebuild first, with a page-recovery fallback for severe damage.
Verified results
Each repaired PDF is opened and checked before it's handed back to you.
Stays on your device
Repairs run in your browser, so confidential files are never uploaded.
Why PDFs get corrupted
A PDF ends with a cross-reference table: a map of byte positions for every object in the file. If a download stops early, a USB stick is unplugged during copying, or an app crashes while saving, that map is often the part that goes missing or points to the wrong places. Some email systems and file-sync tools also add stray data to the start of attachments. Readers like Acrobat then refuse to open a file whose pages are actually still intact.
How the repair works
First, every object in the file is read directly instead of trusting the broken index. The document's page tree is reconnected, anything no longer referenced is discarded, and a brand-new file with a correct cross-reference table is written. A second, independent PDF engine then opens the result to confirm every page loads. If the structure is too badly damaged for that, a more forgiving reader recovers whatever pages it can display.
Fixing bloated files
PDFs that have been edited, annotated, and re-saved many times often keep every old version of changed objects inside the file. They still open, but they're much larger than they should be and sometimes slow or unstable. Running them through Repair PDF strips out unreachable data and stores the rest efficiently — a quick way to clean up a file before archiving or sharing it.
When a repair isn't possible
If the page content itself has been overwritten — for example, a file that was only partly downloaded and is mostly empty — no tool can bring back what was never saved. In that case, ask the sender to share the file again, re-download it, or check your email and cloud storage for an earlier version.
Pro tip: once your PDF opens again, consider running it through Compress PDF to make it smaller and keep a backup copy somewhere safe.
Frequently Asked Questions
What kinds of PDF damage can be repaired?
The most common problems are fixable: a broken or missing cross-reference table, files cut short by an interrupted download or email, stray data in front of the PDF header, and documents bloated by leftover data from repeated edits. Files whose page content itself has been overwritten can only be partially recovered.
Why does my PDF say it's damaged or won't open?
Usually because the file was not transferred completely — an interrupted download, a full disk, an email system that altered the attachment, or an app that crashed while saving. The pages are often still inside the file; the index that tells readers where to find them is what's broken.
What does "recovered as images" mean?
When the structure is too damaged for a lossless rebuild, PDFDoco falls back to a more forgiving reader that can still display the pages, and saves each page as an image. The pages look the same, but text can no longer be selected or searched.
Can Repair PDF make my file smaller?
Often, yes. PDFs that have been edited and saved many times can accumulate unused data. The rebuild keeps only what the document actually uses and stores it efficiently, which frequently reduces the size. For bigger savings, use Compress PDF afterwards.
Can it repair a password-protected PDF?
Encrypted files need to be unlocked first so their contents can be read. Use Unlock PDF with the password, then run the unlocked copy through Repair PDF if it still has problems.
Is my original file changed?
No. Your original file is never modified. The repaired version is downloaded as a new file ending in -repaired.pdf, so you can compare the two.