The best free PDF compressor: how to judge one and what to use

What to judge a PDF compressor on

Size reduction is the obvious measure, but it is the least useful on its own. Any tool can make a file tiny by turning the pictures to mush. Judge a compressor on six things together.

First, how much smaller the file gets for the kind of PDF you have. A text-only PDF barely shrinks anywhere; a scan or a photo-heavy brochure can lose 70 to 90 percent. Second, readability afterward: can you still read small text in a scanned page, and do photos look acceptable at normal zoom? Third, limits: files per day, maximum file size, files per batch. Fourth, privacy: where the file goes, whether an account is needed, and how long the file is kept. Fifth, batch: can you compress ten files at once? Sixth, watermark: a free tool that stamps its name on your output is not free in any sense that matters.

• Size reduction for your type of PDF, not a marketing average
• Readability of small text and photos after compression
• Limits: daily cap, maximum file size, files per batch
• Privacy: upload or local, account or not, retention time
• Batch support
• No watermark on the output

How to test a PDF compressor yourself

Do not trust a comparison table, including this one, over a test with your own file. The method below takes a few minutes and works for any tool.

Use two files: a scanned document (a few pages from a phone scanner app) and a report with text and a few photos. Those two cover most real cases. If you only have one, use the one you actually need to send. The steps below work for DocGopher's Compress PDF, Preview, or any other tool.

1. Note the original size of each file and the limit you need to hit (for example 10 MB for a court portal, 25 MB for email).
2. Run each file through the compressor with its default or recommended setting. Note the output size.
3. Open the output and zoom to 200 percent on the smallest text and on one photo. If you cannot read a footnote or a date stamp, the setting is too strong.
4. Search the compressed file for a word you know is in it. If search fails on a file that was searchable before, the tool rasterized the text, which is a bad sign.
5. Check the output for a watermark on any page, and check the tool's privacy page for how long files are kept.
6. Compress a batch of five files if you do that often. Note whether the tool allowed it on the free tier and how long it took.
7. Repeat with a stronger setting only if the default did not reach your limit.

DocGopher Compress PDF: what it actually does

DocGopher's Compress PDF makes PDFs smaller for email and upload while keeping them readable. It is free, with no sign-up and no watermark. Each file can be up to 300 MB and you can compress up to 50 files in one batch, which covers a folder of scanned receipts or a month of invoices in one go. It works in the browser on a phone or a computer, so a scan on your phone can be compressed before you email it from the same device.

On privacy: files are processed in memory on DocGopher's own servers and deleted after 30 minutes. There is no account and no stored history. It does not use third-party processing services.

What it does not do, so you are not surprised: it has no desktop app, no cloud storage, and it will not turn a 200 MB photo album into a 1 MB file without visible quality loss, because no compressor can. If your file is mostly text and already small, the saving will be modest. If it is a scan, expect a large drop.

Free compressors already on your computer

Preview on a Mac: open the PDF, choose File, then Export, and set Quartz Filter to Reduce File Size. It is free and offline. The built-in filter is aggressive with images and can make scanned text look soft, so run the readability check. Compressing one file at a time is the other drawback.

Microsoft Word on Windows or Mac: if you wrote the document, open the source file and use Save As PDF with the Minimum size (publishing online) option. Word recompresses the pictures as it writes the PDF. This only works for documents you have in Word; opening an existing PDF in Word and re-saving it can change the layout.

Microsoft Print to PDF and Chrome's Save as PDF do not compress existing PDFs in a meaningful way; they re-print the pages, and the output is often larger. Use them to create a PDF, not to shrink one. On an iPhone there is no built-in compressor for PDFs; the Files app can share a PDF but not reduce it, so a browser tool is the practical route.

Online compressors and your privacy

Every online compressor uploads your file to a server. That is fine for a brochure and worth a moment's thought for a tax return or a medical record. Three questions settle it: where does the file go, how long is it kept, and does the site need an account?

Checked on the sites' own pages on 11/09/2026: Smallpdf states files are automatically deleted an hour after processing unless you choose to store them, and iLovePDF states it keeps files for a maximum of two hours so you can download them. DocGopher deletes files after 30 minutes. All three let you compress without creating an account. For anything you would not email unencrypted, use Preview or another offline tool instead, so the file never leaves your computer.

A note on the freemium sites' free tiers, also checked in November 2026: on Smallpdf, only the Basic compression level is free; the Moderate and Strong levels are marked Pro, and the free plan limits tasks per day. On iLovePDF, the free Compress PDF takes 2 files per task of up to 200 MB each, with batch sizes up to 10 on Premium. Both are solid compressors if those limits suit you.

Other kinds of free compressors

Beyond the tools above, free compressors fall into a few categories. Freemium all-in-one PDF sites compress well on the default level and sell the stronger levels or batch size. Single-purpose compressor sites do one job with fewer limits and fewer safeguards; read their privacy page. Free desktop PDF readers and editors often include a reduce-size or optimize command, with results that vary by product. Open-source command-line tools give the most control over image resolution and quality and are the right choice for a technical user with hundreds of files.

If a PDF is still too large after compression, change the problem instead. Split the PDF into two parts under the limit. Convert color scans to black and white with Grayscale PDF, which cuts size and ink. If the PDF was built from photos, compress the pictures first with Compress image and rebuild the PDF with Image to PDF. Delete the pages you do not need.

When compression will not help

Compression works on images and on unused data inside the file. It does little for a PDF that is already mostly text with vector graphics, which is why a 400 KB contract rarely drops below 300 KB anywhere. It also cannot rescue a scan made at 600 dpi in color when a 200 dpi black-and-white scan would have been right; rescanning at a sensible setting beats any compressor.

Embedded fonts, attached files and form data also take space that compression leaves alone. If the limit you face is strict and the file will not move, split it or send a link to a shared drive instead.

Verdict

For most people, the best free PDF compressor is whichever one passes the five-minute test on your own file. On that test, DocGopher's Compress PDF is a strong default: free, no sign-up, no watermark, no daily cap, files up to 300 MB, 50 files per batch, deleted after 30 minutes. Preview is the right choice on a Mac when the file must not leave your computer, with a check on text sharpness. Word's Minimum size export is the right choice for documents you authored.

The freemium sites are good compressors too, and as of November 2026 their free tiers are enough for one or two normal files a day. The moment you need a batch, a stronger level or a large file, you are either paying or switching, and this guide gives you the free switch.