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structure onlyHow does PDF compression work?
PDF file size typically comes from embedded images (often the biggest factor), duplicated or inefficiently stored internal objects, and how the underlying binary data is packed. A full compressor also downsamples images; this tool handles only the last part — it re-saves your PDF with object streams enabled to remove structural bloat, but does not recompress the images inside it.
When you will and won't see a reduction
You'll see the biggest gains on PDFs produced by older tools or repeatedly re-saved files with redundant internal objects. Because this tool doesn't touch images, an image-heavy scanned PDF will shrink only modestly. A PDF that's already well-optimized or mostly text may show little to no change — that's expected, not a failure.
Frequently asked questions
Why didn't my PDF get much smaller?
This tool optimizes the PDF's internal structure (using object streams to reduce overhead) rather than recompressing embedded images. If most of your file's size comes from high-resolution images — which is common for scanned documents — structural optimization alone won't reduce it by much. A PDF that's already well-structured or mostly text may also show little change simply because there wasn't much redundancy to remove.
Does this tool recompress or downsample the images inside my PDF?
No. It only reorganizes the PDF's internal object structure — it doesn't touch image resolution or quality at all, so there's zero visual quality loss anywhere in the document. If you need to shrink an image-heavy PDF significantly, the image data itself needs recompressing, which is outside what this structural optimizer does.
Is this safe to use on scanned or image-heavy PDFs?
Yes, completely safe — since it never modifies image data or visible content, there's no risk of quality loss or corruption. You just shouldn't expect a large size reduction on such files, since their size is dominated by images rather than structural overhead.
What's a safe PDF size for email attachments?
Most major email providers cap attachments around 25 MB (Gmail, Outlook.com), though some enforce lower limits like 10-20 MB, and recipients' inboxes may have their own restrictions. If your compressed PDF is still too large to email, splitting it into smaller parts (see the Split PDF tool) or recompressing embedded images with a dedicated tool are the next steps.