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A single PDF file · processed locally
Upload a PDF to preview its first page before compressing.
How 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. This tool handles both: it decodes embedded JPEG and raw bitmap images and re-encodes them as JPEG at your chosen quality — the same canvas-based approach as the Image Compressor — and it re-saves the file with object streams enabled to remove structural bloat. An image is only replaced if the recompressed version is smaller.
When you will and won't see a reduction
You'll see the biggest gains on image-heavy or scanned PDFs, since photos usually dominate file size and now get recompressed alongside the structural cleanup. A PDF that's already well-optimized, mostly text, or built from vector graphics may show little change since there's little left to compress. Some images are deliberately left untouched to avoid any risk of visual corruption — ones with transparency (a soft mask or color-key mask), CMYK or indexed color, or less common encodings like CCITT fax or JPEG2000.
Frequently asked questions
Why didn't my PDF get much smaller?
This tool recompresses embedded JPEG and raw bitmap images at your chosen quality and re-saves the file's internal structure with object streams. If your PDF is already well-optimized, mostly text, or its images use encodings this tool intentionally skips (CCITT fax, JPEG2000, CMYK, indexed color, or anything with transparency), you may see little change — that's the safety trade-off, not a bug. Try lowering the quality slider for a bigger reduction on photo-heavy files.
Does this tool recompress or downsample the images inside my PDF?
Yes — embedded JPEG and raw bitmap images are decoded and re-encoded as JPEG at the quality you choose; pixel dimensions aren't changed, only compression level. As a safety check, an image is only replaced if the recompressed version is actually smaller, so nothing is ever made larger. Some image types (transparent, CMYK, indexed-color, CCITT fax, JPEG2000) are left untouched, since safely recompressing them needs more than a canvas re-encode.
Is this safe to use on scanned or image-heavy PDFs?
Yes, with one trade-off to know: unlike the structural cleanup (always lossless), image recompression is lossy. If scanned text needs to stay sharply legible, keep the quality slider high — 90% or above keeps artifacts minimal, though at very high settings an image sometimes won't shrink at all, in which case it's simply left as-is rather than made larger.
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.