2026-04-30 · 9 min read

How to Compress a PDF Without Losing Quality

Email attachment limits, slow web uploads, storage caps in Google Drive — there are lots of reasons to shrink a PDF, and lots of bad ways to do it. Here’s what actually drives PDF file size, four methods that work, and the trade-offs you should expect when you push compression hard.

What makes a PDF big in the first place

About 90% of the bytes in a typical PDF are in three places: embedded fonts, raster images, and scanned page images. Plain text takes almost no space; a 100-page text-only PDF is often under 500 KB. Once you add high-resolution photos or scans, the file balloons quickly — a single 12-megapixel photo embedded uncompressed can be bigger than the rest of the document combined.

The implication: compression strategies that target images and fonts will give you the biggest savings. If your PDF is already mostly text, there’s usually only modest compression to be had.

Method 1 — Use a browser-based PDF compressor

For most people, the fastest path is a free in-browser tool. The good ones do three things: re-encode embedded images at a lower DPI (typically 150 DPI for screen, 300 DPI for print), switch image compression to an efficient codec (JPEG2000 or modern JPEG), and subset embedded fonts so unused glyphs are dropped.

Look for a tool that runs locally in the browser if your PDF contains sensitive content — once you’ve uploaded a tax return or medical record to a server, you have to trust that operator’s privacy policy. Tools like ours process files entirely on-device.

Method 2 — Compress in Adobe Acrobat

If you already have Acrobat Pro, File → Save As Other → Reduced Size PDF is the fastest option. For more control, use Optimize PDF which lets you tune image downsampling, font subsetting, and metadata stripping per asset class. Acrobat’s output is generally the highest fidelity, but the savings vary widely depending on what was in the original file.

Method 3 — “Print to PDF” with lower quality settings

Both macOS and Windows can re-print a PDF to a new PDF at lower quality.

• macOS: open in Preview, File → Export, choose PDF, and pick a Quartz Filter such as “Reduce File Size.”
• Windows: File → Print → choose “Microsoft Print to PDF,” and reduce the print quality before saving.

This is fast and free but blunt — the default reduce filters often crush image quality more than necessary. Acceptable for emailing a résumé, less so for a portfolio.

Method 4 — Command line with ghostscript

For batch jobs or automation, ghostscript gives you fine control. The standard recipe:

gs -sDEVICE=pdfwrite \
   -dPDFSETTINGS=/ebook \
   -dNOPAUSE -dQUIET -dBATCH \
   -sOutputFile=output.pdf input.pdf

The key knob is -dPDFSETTINGS. /screen is most aggressive (72 DPI), /ebook is a good balance (150 DPI), /printer is press-quality (300 DPI). Try /ebook first and only step up if quality is unacceptable.

How small should you go?

A few practical targets:

• Email attachments: aim for under 10 MB to clear most provider limits, ideally under 5 MB.
• Web uploads (job applications, government forms): 2–5 MB is a common ceiling.
• Print: stay at 300 DPI for any image you want to look good on paper. Smaller savings, but worth it.

When compression backfires

Two things to watch out for:

• Scanned PDFs without OCR: aggressive compression can make fine text unreadable. If the PDF is a scan of paper, run OCR first; the OCR version is usually smaller and better.
• Form fields: some compressors flatten interactive form fields into static images. If the recipient needs to fill the form, verify the output before sending.

A 30-second decision tree

1. One file, in a hurry, sensitive content → in-browser tool.
2. Highest fidelity, willing to pay → Acrobat Pro.
3. Quick reduce, no installs, on a Mac → Preview Quartz filter.
4. Hundreds of files or scripted pipeline → ghostscript.

Need to get from PDF to an editable Word document instead? Use our free PDF to Word converter — it runs entirely in your browser, just like a good compressor should.