PDFs balloon. A 10-page document that’s mostly text can be 5MB if it has images. A scanned book with photos can be 100MB+. Email services reject attachments over 25MB. Cloud storage works but costs money. The fix: compress the PDF.

Here’s how to shrink a PDF without losing quality, free, in 2026.

Why PDFs get so big

PDFs that balloon usually have one of these:

High-resolution images — a single 4MB photo on one page makes the whole file huge
Scanned documents — a 30-page scan can be 50-100MB because every page is treated as a full image
Embedded fonts — fonts included in the PDF for visual fidelity (good for sharing, expensive for size)
Duplicate resources — same image referenced multiple times, re-embedded each time
Metadata bloat — version history, XMP data, edit history preserved
Form fields and JavaScript — interactive PDFs include code

For text-only PDFs (exported from Word, Google Docs, etc.), compression gain is small (~10-20%). For scanned PDFs and image-heavy documents, compression can reduce file size by 70%+.

How PDF compression actually works

There are two main techniques:

Image downsampling. Detects images that are way higher-resolution than necessary (a 6000x4000 photo on a page that displays at 800x600) and downsamples them. The visible result looks identical but the file is much smaller.
Lossy image recompression. Re-encodes JPEGs inside the PDF at lower quality. Like JPEG compression, you lose some detail but the file gets dramatically smaller.

Text, fonts, and metadata usually stay intact. Compression is very selective — only the parts that benefit get touched.

Method 1: Use a browser-based PDF compressor (fastest, most private)

→ Try our free PDF compressor

What you do:

Open the tool in your browser
Upload your PDF (drag and drop or browse)
The tool runs entirely in your browser using pdf-lib
Get a compressed PDF
Done — your PDF never left your device

Browser-based compression works because pdf-lib is a full PDF manipulation library compiled to WebAssembly. We don’t need a server — the same operations happen locally that would happen on a server.

Typical gains:

Text-only PDFs: 10-20% smaller
PDFs with image content: 50-80% smaller
Scanned PDFs: 60-90% smaller

Method 2: Adobe Acrobat (industry-standard but not free)

If you have an Adobe Acrobat subscription:

Open the PDF in Acrobat
Tools → Compress PDF
Choose quality level
Save the compressed version

Acrobat’s compression is excellent. The “Reduce File Size” preset does what most people want. Power users can dive into individual image-by-image settings.

This is the best quality option but requires a subscription.

Method 3: macOS built-in “Reduce File Size” (free for Mac users)

If you’re on a Mac:

Open the PDF in Preview
File → Export
Choose “Reduce File Size” as the Quartz Filter
Save

macOS’s built-in compression is surprisingly good for the price (free). The “Reduce File Size” filter does image downsampling + JPEG recompression in one pass.

Limitation: it doesn’t give you options. You get whatever the system thinks is the right tradeoff.

Method 4: Ghostscript (free command-line tool, devs)

For developers and power users, Ghostscript is the standard:

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
   -dPDFSETTINGS=/screen \
   -dNOPAUSE -dQUIET -dBATCH \
   -sOutputFile=output.pdf input.pdf

The /screen flag sets low quality (smallest files). Other options:

/screen — 72 DPI images (smallest files, decent for screen reading)
/ebook — 150 DPI images (good balance)
/printer — 300 DPI images (high quality, larger files)
/prepress — highest quality (largest files)

Ghostscript is free, open source, and produces excellent results. Downside: command-line tool, requires install, no nice UI.

Method 5: Smallpdf.com and similar (web services)

Popular online PDF compressors:

Smallpdf.com — clean UI, decent compression, requires upload
iLovePDF.com — multiple PDF tools, requires upload
PDF Compressor (pdfcompressor.com) — focused tool, requires upload
Soda PDF Online — fully featured, requires upload

All of these upload your PDF to their servers to process. Privacy implications:

They have your document on their infrastructure
They claim to delete after processing (verify the privacy policy)
Most don’t use your docs for training, but some reserve the right

For confidential documents (legal, medical, financial), prefer Method 1 (browser-based). For non-sensitive files, online tools are convenient.

What to do with massive scan PDFs

If you have a 100MB scanned document, basic compression might only get you to 60MB. To go further:

Re-scan at lower DPI. If you can re-scan, 200 DPI (vs 600 DPI default) cuts file size by ~9x.
Convert to grayscale. Color scans are 3x larger than grayscale. If the document doesn’t need color, this is huge.
Split into chapters. Easier to email, easier to view.
Convert to a different format. For text-only scans, OCR + a new PDF is often smaller than the original scan.

Smart ways to manage many PDFs

If your work involves lots of PDFs (researcher, lawyer, designer, dev), here are the management tactics:

Cloud with offline sync — Dropbox, iCloud, OneDrive. Get cloud access without uploading each PDF individually.
PDF aggregator — Devonthink, Papers, Zotero for research; Eagle for designers. They handle compression in the background.
Tags and folders — even a clean folder hierarchy beats a messy Downloads folder.
Version control — keep originals separately from compressed versions. You can’t un-compress.

Batch compression

If you have many PDFs to compress, batch processing matters:

Browser-based tools: drag multiple files at once
Mac Preview: open each, batch export via Automator
Ghostscript script: loop over files in a folder
Adobe Acrobat Pro: batch actions in the Actions panel

Our tool compresses one PDF at a time. If batch is critical for your workflow, the offline tools (Ghostscript, Acrobat) are better. For occasional compression, browser-based tools are perfect.

Try it now

Got a PDF that’s too big to email?

Open our PDF compressor in your browser
Upload the PDF
Get a compressed version — file never left your device

Total time: 5 seconds.

Related tools: PDF Compressor · Compress PDF · Shrink PDF · Make PDF Smaller

How to Shrink a PDF File Without Losing Quality (Free, 2026)