Compress PDF for Email Attachments
Most email providers cap attachment size — Gmail rejects anything over 25MB, and Outlook caps at 20MB, so a PDF just slightly over the limit will bounce back undelivered instead of sending. Compressing embedded JPEG images (the usual culprit in oversized PDFs) at the Medium or High level below is often enough to get back under those limits. If your PDF is still too large after compression, it's likely made up mostly of non-JPEG images or scanned pages that this tool can't shrink further — in that case, splitting it into smaller parts or sharing a download link instead of an attachment is the more reliable option.
Your PDF is processed directly in your browser's memory using a client-side library — nothing is uploaded to any server.
How to use this PDF compressor
- Select a PDF file.
- Pick a compression level and click "Compress & Download".
- The reduced file downloads automatically, and you'll see exactly how much size was saved.
How does this actually reduce file size?
Document metadata (author, title, producer info) is stripped, and the file structure is re-optimized. Any embedded JPEG images are downsampled and recompressed at the level you choose — this is where most of the size reduction comes from on image-heavy PDFs, since photos are usually the largest part of a file by far.
How much smaller will my file get?
It depends entirely on the content. PDFs with embedded JPEG photos can shrink dramatically — commonly 50-80% — since those images get downsampled and recompressed. A text-only PDF with no images will only shrink a small amount (typically under 10%), from removing metadata and optimizing the file structure, since text content is already compact.
Does this work on all embedded images?
Only JPEG images are recompressed. PNG images and other raster formats embedded in the PDF are left untouched and don't contribute to the size reduction — this is a limitation of what can be reliably decoded and re-encoded client-side.
Why PDFs get so large in the first place
A PDF's file size is almost never driven by its text — plain text, even many pages of it, compresses to a tiny fraction of a megabyte, since text is inherently compact data. What actually drives file size is embedded raster images: a PDF containing a handful of photos taken straight from a modern phone or camera, each several megapixels at full resolution, can easily reach tens of megabytes, since those images are usually included at their original camera resolution regardless of how large they're actually displayed on the page. Scanned documents are the extreme case — a "scanned" PDF is typically just one full-page image per page with no real text underneath at all, which is why scanned documents tend to be dramatically larger than the same content typed as real text would be.
Why only JPEG images get recompressed
This tool specifically targets embedded JPEG images because JPEG is a lossy format to begin with — recompressing it at a lower quality setting is a well-defined, predictable operation with a clear size-versus-quality tradeoff. PNG and other lossless formats embedded in a PDF are left alone because converting them to a lossy format would be a much more aggressive, format-changing operation than "compression" implies, and could produce unexpected visual results for images that specifically needed lossless quality (like scanned line art, diagrams, or screenshots with text) in the first place. This is a deliberate, conservative choice: this tool won't silently degrade an image type it wasn't asked to touch.
Metadata stripping and file structure optimization
Beyond image recompression, a meaningful amount of a PDF's bloat can come from things that have nothing to do with what's visibly on the page: metadata fields recording the authoring software, editing history, and document properties; unused or duplicate font subsets embedded multiple times across a document's editing history; and, in PDFs that have been edited and re-saved repeatedly, an accumulation of "incremental update" data where each edit appends new data to the file rather than rewriting it cleanly. Stripping metadata and rebuilding the file structure from scratch removes this accumulated overhead, which is why even a text-only PDF with no images can sometimes shrink by a small amount, purely from cleanup rather than any change to image quality.
Why compressing an already-compressed PDF barely helps
A PDF that's already been through compression (by this tool, by another tool, or by whatever software originally exported it) generally won't shrink much further on a second pass. If the embedded JPEG images were already recompressed at a similar quality level, applying compression again mostly just risks additional quality loss on those images without meaningfully reducing size, since there isn't much "wasteful" data left to remove. The one exception is a PDF that's been edited and re-saved multiple times by desktop PDF editing software, which can accumulate the kind of incremental-update bloat described above — in that specific case, a fresh compression pass can still recover meaningful size even if the images themselves are untouched.
Limitations of this tool
This compressor works entirely in your browser's memory using a client-side PDF library, which shapes what it can and can't do: it recompresses embedded JPEG images and strips metadata, but it doesn't touch vector graphics, embedded fonts, or PNG/other raster formats, and it doesn't perform OCR or convert scanned page images into real searchable text — a scanned PDF stays exactly as large as its underlying page images allow, since there's no text to compress in the first place. It also doesn't support PDF/A archival format preservation or encrypted/password-protected PDFs, both of which require handling this tool's straightforward compress-and-rebuild approach isn't designed for.