Compress PDF
Reduce the size of a scanned document
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PDF document · Up to 100 MB
How do you reduce the size of a PDF?
The tool redraws the page images at a lower quality and shrinks the file that way. It is meant for scans, which are made of images. If the result is not smaller than the file you supplied, the tool will not hand it over: you get your original back untouched, and the failure to shrink is stated plainly.
What compression does not do
- It does not shrink a text document — in that case the original is returned.
- It does not keep the text layer: the result is made of images.
- It never returns a file larger than the one you gave it.
Worked example: a text document did not compress
A 10-page text document was sent to the compressor. The redrawn version came out several times larger than the original — roughly 24 KB against 4.5 KB. The tool therefore rejected the result and returned the original untouched. Repeating the test on a document that had already been turned into images ended the same way: on small files, redrawing yields nothing.
Sending a scan that exceeded a portal limit
Journal portals and conference systems cap the size of an uploaded file, while dissertation appendices often run to dozens of leaves scanned at high resolution and go over that ceiling. In such a document the size comes from the page images rather than from text, so redrawing them at a lower quality produces a genuine result. One condition matters: the compressed copy is for submission only, and the original scan must stay in your archive, because a redrawn image cannot be restored. Never compress the file that goes for a plagiarism check: a redrawn document keeps no text layer, and the checking system will not be able to read text from it.
Questions about compressing PDFs
Why did nothing change?
Because the redrawn version did not come out smaller than the original. That is ordinary for text documents: text is already stored very compactly, while an image takes more room. Rather than hand over a larger file, the tool returns the original.
Can text still be searched after compression?
No. Pages are redrawn as images, so the text layer is lost: searching, copying and screen readers all stop working. That is exactly why the tool is meant only for documents that were already scans.
Which level should I choose?
The low level gives the smallest file but blurs small lettering; the high level keeps more detail. For official paperwork start at the medium level and check the result at full zoom on screen.
Is there another way to shrink a scan?
Yes: removing surplus pages or splitting the document into parts is often enough. Lowering the resolution at the scanner setup stage also helps — and it gives better quality than redrawing.