PDF Compressor

How to do it

1. Press Choose PDFs, drop them on the page or paste them with ⌘V / Ctrl+V — one PDF or many.
2. Open Settings to pick a Compression level — Recommended is chosen for you, for pages that stay sharp in print; Extreme makes the smallest files, and Low changes as little as possible. The level applies to every PDF in the list.
3. Press Compress (Compress all when there are several PDFs). Each file's row then shows its size before and after and how much it saved; change the level later and the PDFs you've compressed are compressed again.
4. Press Preview on a file's row to compare the original and compressed pages side by side, or at 200% to check fine detail. What changed, under the preview, lists what was done to that file.
5. Download each PDF from its row, or press Download all — from 4 files it's one .zip, or One by one.

Questions

What does each Compression level do?

Extreme brings photos sharper than 125 ppi down to 100 ppi, saves a photo stored without loss as JPEG quality 60 only where that saves 5% or more, and re-saves an existing JPEG at its own size only above quality 70: the smallest files, fine on screen, though detail softens when you zoom in. Recommended brings photos sharper than 250 ppi down to 200 ppi, saves a photo stored without loss as JPEG quality 82 only where that saves 15% or more, and re-saves an existing JPEG at its own size only above quality 90: sharp on screen and in print. Low brings photos sharper than 450 ppi down to 300 ppi, keeps full colour detail and never re-saves an existing JPEG at its own size; a photo stored without loss is saved as JPEG quality 90 only where that saves 30% or more. A photo's resolution is measured as it's placed on the page, and it's only changed where that makes the file noticeably smaller.

What does compressing never change?

Text, vector drawings and fonts (none is ever removed), links, form fields and what's filled in, tags, bookmarks, attachments and layers stay exactly as they are. Charts, screenshots and other pictures with few colours are kept lossless at every level; only photos are ever saved as JPEG.

Is anything removed from the PDF?

Page thumbnails, at every level. At Recommended and Extreme, also Adobe Illustrator's editing data and the metadata attached to single images; the document's own title, author and metadata are kept. The compressed copy isn't set up for Fast Web View, and earlier saved versions kept inside the file aren't carried over.

Why didn't my PDF get smaller?

When compressing wouldn't make a file smaller, you get your original back: its row says so, and Download and Download all give the original under its own name. That happens with PDFs that are already optimised or mostly text, with JPEG photos over 32 megapixels that the level doesn't bring down in resolution, and with pictures the tool leaves as they are — CMYK JPEGs, JPEG 2000, and black-and-white scans.

Can I compress a digitally signed PDF?

Yes, but any change to a signed PDF breaks its signature, so its row warns you; keep the original wherever the signature matters. If compressing would save less than 5%, the tool keeps your original instead. Adobe Reader's extra features (such as saving filled forms) won't be switched on in a compressed copy.

Does it work with PDF/A, PDF/X and older PDFs?

Yes. A PDF/A-1 file, or a PDF/X-1a or PDF/X-3 print file, keeps its metadata and is saved in the older file layout its standard requires, but the result isn't checked against the standard again — keep the original wherever conformance is required, such as for a print shop's preflight. Any other PDF older than version 1.5 is saved in the newer, smaller layout at Recommended and Extreme, and keeps its own at Low.

How many PDFs can I compress at once, and how large?

As many as you like, each up to 250 MB and 2,000 pages. They're compressed one at a time; a very large or complex PDF can still be too much for a browser tab, and its row says so. From 4 files Download all makes one .zip — a file that couldn't be made smaller goes in as your original. Each compressed copy is named like report-compressed.pdf.

Are my PDFs uploaded?

No. They're read, compressed and previewed in your browser tab and never leave your device. Only the JPEG encoder and the page previewer are downloaded, from OpsDrawer itself, the first time they're needed.