Compress PDF

Make a PDF smaller without wrecking it

Most oversized PDFs have the same problem: images stored at far higher resolution than anyone will ever see. A phone photo dropped into a report carries 12 megapixels into a page that displays maybe one. This tool rebuilds your PDF with Ghostscript and resamples those images down to a resolution you choose, which is where nearly all the savings come from.

Text is never touched. It stays as real text, sharp at any zoom level, because compression only affects images and the file's internal structure. The upload limit is 10 MB.

Over the 10 MB upload limit? You can split the PDF into smaller files first and compress the parts separately.

What the three levels actually do

The levels map directly to Ghostscript's print presets, so they mean something concrete:

• High quality keeps images at 300 dpi, which is print resolution. The file shrinks a little from structural cleanup, but pictures survive a trip to the printer.
• Medium quality resamples images to 150 dpi. On a screen you won't see the difference; the file usually will. This is the default and the right choice for email.
• Low quality goes to 72 dpi, the old screen standard. Images get visibly softer if you zoom in, but the size drop is dramatic.

How much smaller will it get?

Honest answer: it depends entirely on what's inside, and the range is enormous. In our own testing, a 4.7 MB PDF made of two full-page photos came out at 70 KB on the strongest setting - a 98% drop. Meanwhile, across all the real files people have compressed here, the average saving is closer to 13%.

Why so far apart? Because most uploads are text documents that were already efficient. A contract written in Word and exported to PDF has almost nothing left to squeeze. A scan, a photographed receipt, or a slide deck full of screenshots is the opposite: mostly oversized image data, and that's where 70-95% reductions are normal.

Quick rule of thumb before you upload: if the PDF started life as a scan or contains photos, expect a big win. If it's pure typed text, expect a modest one.

When the file comes back bigger

It happens, and it's worth understanding. Ghostscript doesn't trim the existing file - it rebuilds the whole PDF from scratch. If your original was already tightly optimised and its images already sit below the target resolution, the rebuilt version can come out a few percent larger than what you uploaded. We saw exactly that in testing: an already-efficient 4.66 MB file came back at 4.88 MB on the gentlest setting.

If that happens to you, the answer is simple: keep your original, or retry with a stronger level. Nothing went wrong - there was just nothing left to save at that quality target.

Where the bloat usually comes from

Knowing the source of a PDF tells you a lot about how it will compress. Phone scanning apps are the worst offenders: they save each page as a full-resolution photo, so an 8-page scan can easily hit 10 MB. PowerPoint exports come second, because every slide background and pasted screenshot travels at its original size. Word and Google Docs exports sit at the other end - they're usually lean already, unless someone pasted photos straight from a camera roll.

There's a practical lesson in that: if you control how the PDF gets made, half the battle is over. Scanning at 150 dpi instead of 600, or resizing photos before they go into a document, beats any after-the-fact compression.

The email limits you're actually fighting

For reference, since this is why most people are here: Gmail caps attachments at 25 MB, Outlook.com at 20 MB, and many corporate mail servers at 10 MB. But the trap is that the limit applies to the encoded message, which runs about a third larger than the file itself - so a 19 MB attachment can bounce from a 25 MB inbox. Aim comfortably under the ceiling, not just below it.

A real example

Say a rental agency wants your signed lease back by email, and your phone's scan of the 8-page document weighs 9 MB. Their inbox caps attachments at 10 MB, but yours caps outgoing mail at 5. Upload the scan here, leave the level on medium, and you'll typically get back something around 1-2 MB - readable, printable, and small enough to send without splitting it across two emails like it's 2004.

Check it before you send it

Open the compressed file once before it goes anywhere important. Look at any page with a photo, a signature, or fine print, and zoom to the level a reader actually would. If a stamp or signature has gone muddy on the low setting, run it again on medium. The re-run costs ten seconds; a rejected document costs a day.

A few things that won't work

Password-protected PDFs fail with an error - Ghostscript can't open what it can't read, so remove the password first. And don't expect miracles on a PDF that another compressor already squeezed: compression stacks poorly, and the second pass mostly just softens images further for little gain.

When a different tool fits better

And if the real reason you're fighting file size is that you need to edit the document anyway, convert it to Word instead and work on the text directly.

Sending several small PDFs together? Merge them into one document first, then compress the result - one clean attachment beats five.

On privacy: your PDF is uploaded over SSL, rebuilt, and deleted from the server as soon as the job finishes. The compressed copy exists just long enough for you to download it. Nothing is stored, read, or shared.