PDF Tools

Repair PDF

Loads a PDF with the pdf-lib library and saves it again as a fresh file named repaired.pdf. This rebuilds the file structure and often fixes minor damage such as a bad cross-reference table, but it cannot recover content that is truly missing.

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Process

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Up to 1 files

This will attempt to fix:

Corrupted PDF structure
Missing or invalid objects
Broken cross-reference table
Invalid stream data

Works by loading and re-saving the PDF with pdf-lib, which often repairs common issues.

How to Use

1Drop one PDF onto the upload area or choose it from your device.
2Click the Repair PDF button and wait for the Repairing PDF progress message to finish.
3Download the result, which is named repaired.pdf.
4Open the new file and check every page. If it still will not open, the damage is beyond what this tool can fix.

About this tool

Updated September 19, 2026

What repairing actually means here

The PDF is parsed and written out again as a clean new file, which rebuilds its internal structure.

A PDF keeps an index of where everything in the file lives. When that index becomes inconsistent — a truncated download, a crash during save, a program that wrote the file badly — a reader may refuse to open a document whose content is perfectly intact. Reading it and writing a fresh copy regenerates that index correctly, which is why this fixes a surprising number of files that looked lost.

What it cannot do

It cannot invent content that is not in the file. If pages were never downloaded, they stay missing.

Repair here means fixing how the file is organised, not restoring data. A partial download is the clearest example: the bytes that never arrived cannot be reconstructed, so those pages are gone whatever you run. The same applies to a file damaged in storage — if the page content itself was corrupted, rebuilding the structure around it will not bring the content back.

Whether it worked

Open the result and scroll through every page. A file that opens is not necessarily a file that is complete.

The useful test is not that the document opens but that the pages are all there and render properly. Check the page count against what you expect, and look at the last page in particular, since truncation damages the end of a file first. If the repaired copy opens but is short, the missing part was never in the file you had.

It also tidies files that were never broken

Running a healthy PDF through produces a clean rewrite, which sometimes resolves odd behaviour in other tools.

If another program is refusing a file or producing strange results, a rewritten copy is a fast thing to try before anything more involved. It occasionally changes the file size in either direction, because the structure is rebuilt from scratch. Nothing on the pages is altered, so this is a safe first step when something is behaving oddly and you cannot explain why.

A Guide to the PDF Tools on Synthixx and What Each Does Well
Every PDF tool on Synthixx grouped by job, with one honest sentence on each, its main limitation, and a clear list of what the site does not offer.

Features

Accepts one PDF per run (maxFiles is 1).
Repair method is a plain load and re-save with pdf-lib, which rebuilds the file's internal structure.
Can help with a broken cross-reference table or slightly malformed objects that pdf-lib is able to read.
Runs in your browser; the file is not uploaded.
Per-file size limit of 200 MB from the standard tool pipeline.
Output is a new PDF called repaired.pdf; your original file is untouched.

FAQ

What kind of PDF damage can this fix?

It opens the file with pdf-lib and writes it out again, so the internal object table and cross-reference data are regenerated. That can help when a viewer complains about a bad xref table or slightly malformed structure, provided pdf-lib can still parse the file.

What can it not fix?

It is not a data-recovery tool. If the file was truncated during download, if page content streams are corrupted, or if pdf-lib itself refuses to load the file, the tool will fail or produce the same broken result. It does not use an external repair engine such as qpdf, and it cannot bring back pages or images that are missing from the file.

Will the repaired PDF look identical to the original?

Usually the pages look the same, because content is carried over rather than redrawn. Because the file is rebuilt, always open repaired.pdf and scroll through it before you delete the original.

Is my PDF uploaded anywhere?

No. The load and re-save happen in your browser with pdf-lib and the file is not sent to a server.

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