Compressing a PDF on Windows

Windows 10 and 11 can open a PDF, print a PDF and create a PDF from any application. They cannot make an existing one smaller. There is no filter in Edge, no option in File Explorer, and nothing in Settings. Searching for one leads to a page of installers and upload sites, which is how most people end up here.

What Windows does have is three things that look like they should work. One does, under a specific condition.

Word's Minimum Size option, which only helps before the PDF exists

When you save a document as PDF from Word, PowerPoint or Excel, the Save As dialog has an Options button (reached through File, Save As, More Options, then Options in the dialog) and under it a choice Microsoft documents as:

• Standard (publishing online and printing), for when the document requires high print quality
• Minimum size (publishing online), for when file size is more important than print quality

Minimum size downsamples the images in the document, which on a Word file with a few photographs can cut the PDF by three quarters. It is the right first move whenever you still have the original document.

It is no use at all on a PDF you received. Word can open a PDF, but it does so by converting it back into a document, which reflows the layout, loses anything it did not understand, and produces a PDF that is not the one you were sent. For a form, a contract or anything signed, do not go that way.

Print to PDF, which makes things larger

The reflex is to open the PDF in Edge, press Ctrl+P and choose Microsoft Print to PDF. This re-creates the document by rendering every page and printing it, and the result is routinely larger than the original: the printer driver rasterises at print resolution, the text may become an image, and the new file has lost the compression the old one had.

It also destroys selectable text on anything it rasterises, which ends search, copy-paste and screen readers silently. Print to PDF is for turning a web page or a receipt into a PDF, not for shrinking one.

Compress in File Explorer, which is a zip

Right-click, Send to, Compressed folder makes a .zip. On a text-only PDF the saving is a few percent; on a scanned PDF, where every page is already a JPEG, it is under 1%. A PDF is already compressed internally, and ZIP has nothing left to find.

What is actually in the file

The useful question on Windows is the same as anywhere: why is it big? Right-click the file, Properties, and look at the size against the page count.

Pages	Size	Almost certainly	The fix
10	200KB	Real text, embedded fonts	Already small; leave it
10	3MB	Text plus a few photos, or a bloated export	Lossless rewrite first, then image quality
10	15MB	A scan at 300 DPI, probably in colour	Resolution, and greyscale
1	8MB	A photograph of a document from a phone	Resolution; this is a photo wearing a PDF

The four reasons a PDF gets large each want a different operation, and only one of them (resolution of scanned pages) is the one every "compress PDF" button reaches for.

The approach that takes a number

Every limit you are compressing for is a number: 2MB for a job portal, 1MB for a government form, 500KB for an upload field that says so. A tool with a preset called Medium cannot aim at a number. The only way to land under one is to encode, measure the real output, and adjust.

That runs in the browser, on the machine, with nothing installed and nothing uploaded. Compress a PDF to 500KB, to 1MB or to 2MB works in Edge, Chrome or Firefox on Windows:

1. Lossless first. The file's internal object streams are rewritten and measured. A Word export, a form, a report with light images often fits right here with nothing lost: text stays text.
2. Rasterise only if needed. When the lossless result is still over, pages are rendered at a scale found by bisection against the actual byte count, so a 2MB limit gets 2MB worth of resolution rather than a preset's guess.
3. Ship the best result that measured under. Not approximately under. Under.

For a scanned document, step 2 is the whole job, and how to pick the resolution a scan actually needs explains why 150 DPI greyscale reads the same as 300 DPI colour on a screen at a tenth of the size.

The arithmetic, worked

A 24-page scanned PDF, 300 DPI colour, 31MB, needed under 2MB for an upload:

Lossless rewrite:         30.4MB   (scans have nothing to pack; expected)
Render at 150 DPI, q0.75:  4.1MB   over
Render at 110 DPI, q0.72:  2.3MB   over
Render at 96 DPI,  q0.70:  1.9MB   fits

That last line is about a sixteenth of the original and reads cleanly at normal zoom. Converting to greyscale on the way (most scans of printed text have no colour worth keeping) would have let the resolution stay higher for the same bytes.

If you do want to install something

There is nothing wrong with a desktop application; the objection is to uploading. PDF24 and similar free tools run locally and work, with the usual caveat that they offer quality presets rather than a byte target, so you will be iterating by hand against your limit. What Acrobat's own Reduce File Size presets do, and why they also cannot take a number, is the same story with a subscription attached.

FAQ

How do I compress a PDF on Windows 11?

Windows has no built-in PDF compressor. If you still have the Word document, re-save it as PDF with the Minimum size option. For an existing PDF, use a compressor that runs in the browser without uploading: it tries a lossless rewrite first, then lowers image resolution until the file measures under your limit. Print to PDF and zipping do not reduce the size.

Does Microsoft Print to PDF reduce file size?

No, and it usually increases it. Print to PDF renders each page through the printer driver and builds a new file, which loses the original's internal compression and may turn selectable text into an image. It is for creating a PDF from a web page or an application, not for shrinking one you already have.

Can I compress a PDF in Word?

Only when saving a document as PDF for the first time: the Options button in the Save As dialog offers Minimum size (publishing online), which downsamples images. Opening an existing PDF in Word converts it back into a document, reflows the layout and may lose parts of it, so it is not a safe way to shrink a PDF you received.

Is there a free PDF compressor for Windows that does not upload my file?

Yes. Modern browsers can render and rewrite PDFs locally, so a page can compress a document entirely on your machine with nothing sent anywhere. The useful ones take a byte target and measure their own output rather than offering Low, Medium and High presets, because a limit is a number and a preset cannot aim at one.