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Compress a PDF
Two approaches, with an honest description of what each costs. Repacking is safe and modest. Rebuilding pages as images is drastic and effective, and it turns your text into a picture of text.
Result
Why browser PDF compression has limits
Most of the weight in a large PDF is images that were embedded at a higher resolution than the document needs. A desktop tool can reach inside, find each image, downsample it and put it back, leaving the text layer alone. That requires decoding every image format a PDF may contain, which is beyond what a browser can reasonably do.
So there are two honest options here. Repack rewrites the file with object streams and drops unreferenced data. It is completely lossless and typically saves somewhere between nothing and 20%, depending on how the file was produced. Rebuild as images draws every page at the resolution you choose, encodes it as a JPEG and assembles a new document. On a scanned or image-heavy PDF this routinely cuts the size by 80% or more.
What image mode costs you
- Text stops being text. It cannot be selected, copied or searched, and a screen reader cannot read it.
- Links, bookmarks, form fields and annotations are lost.
- Sharp text develops slight fuzz, more so at lower detail settings.
For a scanned document, none of that matters and the saving is enormous. For a contract or a CV, it matters a great deal. Choose accordingly.
Common questions
Why did repacking barely change the size?
Because the file was already efficiently written. Repacking removes structural waste, and modern software leaves very little. If you need a real reduction and the document is mostly scanned pages, use image mode.
Can I compress a PDF to a specific size like 500 KB?
Not to an exact target, because the result depends on what is on the pages. Run image mode at medium detail, look at the result, then move the detail and quality controls and run it again. Two attempts usually land where you want.
Is a watermark added?
No. Nothing is added, nothing is stamped, and there is no page limit, because there is no server paying for any of this.
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