Why PDFs break
Most "damaged" PDFs aren't really destroyed: a download stopped early, an email program changed the file, or the program that made it wrote its internal index (the cross-reference table) wrongly. Readers then refuse to open the file, show blank pages, or say it is corrupt.
What Repair PDF does
- It rebuilds the file's structure: the index of objects, their positions and the page tree.
- It keeps every page and object that can still be read.
- If the file is too broken to rebuild, it saves the pages that can still be displayed as pictures, so you at least get their content back.
The result says what happened: problems fixed, the structure rebuilt, or pages recovered as pictures.
If it can't be repaired
- Download the file again or ask the sender to resend it: truncated downloads are the most common cause.
- Missing content (pages that were never saved) can't be brought back by any tool.
- Pages recovered as pictures have no selectable text; run them through OCR PDF to make them searchable again.