Reduce PDF size and fix file problems
A PDF is usually large because of the images inside it, not the text. The tools here attack size and file health from different angles: Compress PDF re-encodes images, PDF to Grayscale drops color, Flatten PDF locks form values, Repair PDF rebuilds a damaged structure and Web Optimize PDF helps large files open faster online.
5 tools
Size versus quality: what really shrinks a PDF
Text and vector graphics take very little space. Scans and photos take a lot, because each page can be a full-resolution image. Compress PDF works on exactly that: it re-encodes embedded JPEG images at a lower resolution and quality, and rewrites the file structure more efficiently, while text and vector artwork stay sharp and selectable. A document that is mostly text, such as a report exported from Word, often shrinks very little because there is little to squeeze.
Start with the Recommended preset and only move to Maximum compression if the result is still too large. High quality is for files you plan to print. If the output would not be smaller, the original is kept and you are told the file was already well optimized. An opt-in mode can turn pages into images to shrink text-heavy scans further, but it makes the text unselectable, so use it only when you accept that.
When each of the other tools applies
PDF to Grayscale renders every page to an image and rebuilds the file in shades of gray. It reduces the size of color scans and suits black-and-white printing, but the text becomes part of the picture; run OCR PDF afterwards if you still need to search it. Flatten PDF turns form fields into fixed page content so values can no longer be edited, and it does not touch comments or other annotations.
Repair PDF is for files that will not open or show errors. It rebuilds the internal structure and can recover many damaged files, but it cannot bring back data that is truly missing. Web Optimize PDF reorganizes the file for fast web view so the first page appears before the whole download finishes; it does not recompress images, so pair it with Compress PDF when size is also a concern.
- Email attachment too big: Compress PDF, then check the result.
- Color scan for black-and-white printing: PDF to Grayscale.
- Form must not be changed after filling: Flatten PDF.
- File will not open or shows an error: Repair PDF.
- Large PDF published on a website: Web Optimize PDF.
Mistakes to avoid
Compressing several times rarely helps and can degrade images further, so keep the original and compress from it once. Compress last, after merging, editing and signing, because later edits can add weight back. And do not expect a size miracle from a text-only file; check the percentage saved before you decide to lower the quality setting.
These tools run in your browser, so the original file is not uploaded. Compress PDF and Repair PDF cannot open password-protected files: unlock them first with Unlock PDF, which needs the password.
Frequently asked questions
Why did my PDF barely get smaller?
Probably because it is mostly text and vector graphics, which are already compact. Compression gains come mainly from images, so a document without large photos or scans has little to shrink. Compress PDF tells you when the file was already well optimized.
Will compression make my PDF blurry?
Text and vector graphics stay sharp, but embedded photos and scans are re-encoded at lower quality and resolution, which can soften them. Try the Recommended preset first and compare; use High quality if the file will be printed.
What is the difference between Compress PDF and Web Optimize PDF?
Compress PDF makes the file smaller by re-encoding images. Web Optimize PDF changes only the file structure so the first page can display before the whole file downloads; the size hardly changes.
Can Repair PDF fix any broken file?
No. It rebuilds the file structure and often recovers documents that will not open, but if parts of the content are actually missing or corrupted, that data cannot be restored. It reports whether problems were found and fixed.