Compress PDF vs. Repair PDF
Shrinking a working file vs. fixing a broken one — different problems entirely.
These solve unrelated problems that share a superficial similarity (both "do something" to an existing PDF). Compress PDF re-encodes embedded JPEG images at a lower quality/resolution to reduce file size, on a PDF that already opens fine. Repair PDF rebuilds a PDF's internal structure to recover from corruption — broken cross-reference tables, malformed object streams — on a file that's damaged, not just large.
Compress PDF
Best for
- A working PDF that's too large to email or upload
- PDFs whose size comes mainly from embedded photos/scans
Trade-offs
- Only recompresses qualifying baseline JPEG images — other content (vector graphics, CMYK images, already-optimized files) won't shrink much
- Does nothing for a corrupted file — it assumes the PDF already opens correctly
Repair PDF
Best for
- A PDF that won't open, or opens with errors in some viewers
- Recovering from broken cross-reference tables or malformed object streams
Trade-offs
- Not a compression tool — any size reduction from rebuilding the file's structure is incidental, not the point
- Can't recover data that's genuinely missing, only structural damage
| Dimension | Compress PDF | Repair PDF |
|---|---|---|
| Problem solved | File is too large | File is damaged/won't open |
| Assumes the PDF | Opens fine already | May not open at all |
| Primary mechanism | Re-encode embedded JPEGs | Rebuild internal object structure |
Verdict
If the PDF opens fine but is too big, compress it. If it won't open or throws errors, repair it first — compression assumes a working file, so running it on a damaged one won't fix the underlying problem.