How to Make a PDF Smaller for Free: Reduce File Size Fast

Quick summary: To make a PDF smaller on Mac, open it in Preview, go to File → Export as PDF, click the Quartz Filter dropdown, and choose “Reduce File Size.” On Windows, print the PDF to Microsoft Print to PDF (which recompresses it), or use Ghostscript for precise control. Online tools work without any install — upload, compress, download. For most PDFs, you can cut file size 40–80% without visible quality loss.

A large PDF slows down email attachments, fails upload limits on portals, and takes longer to load on slow connections. Making it smaller is almost always a one-step operation. The right method depends on whether the PDF is image-heavy (scanned, photo-based) or text-based. You can also upload the PDF to our free AI PDF reader to read and extract content without downloading a large file.

How to make a PDF smaller on Mac

Method 1: Preview — Quartz Filter (built-in, free)

1. Open the PDF in Preview.
2. Go to File → Export as PDF.
3. Click the Quartz Filter dropdown at the bottom of the dialog.
4. Choose “Reduce File Size”.
5. Click Save.

Preview’s “Reduce File Size” filter compresses images inside the PDF to 72 DPI and applies additional compression. It works well for image-heavy PDFs but may reduce quality noticeably on high-resolution scanned documents.

Check the result: Compare the file size before and after. Open the compressed PDF in Preview and zoom in to check image sharpness. If it looks too degraded, use the Ghostscript method below for more control.

Method 2: Ghostscript (Mac, all quality levels, free)

Ghostscript gives you precise control over compression settings. Install with Homebrew:

brew install ghostscript

Then compress the PDF:

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

-dPDFSETTINGS options:

Setting	DPI	Best for
/screen	72 DPI	Smallest file, screen only
/ebook	150 DPI	Good balance, email/web
/printer	300 DPI	Print quality, larger file
/prepress	300+ DPI	Maximum quality, largest file

For most email and web sharing, /ebook produces the best size-to-quality ratio.

How to make a PDF smaller on Windows

Method 1: Print to PDF (built-in)

Re-printing to PDF recompresses images:

1. Open the PDF in any viewer (Edge, Adobe Acrobat Reader, Chrome).
2. Press Ctrl + P to open Print.
3. Set the printer to “Microsoft Print to PDF”.
4. Click Print.
5. Choose a save location and filename.
6. Open the new PDF and check the file size.

This method provides no quality control but works with zero setup. Reduction varies — typically 10–40% for image-heavy PDFs.

Method 2: Ghostscript for Windows (free, precise)

Download the Ghostscript Windows installer (free). After installation:

gswin64c -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 ^
  -dPDFSETTINGS=/ebook ^
  -dNOPAUSE -dBATCH -dQUIET ^
  -sOutputFile=output.pdf input.pdf

Same -dPDFSETTINGS options as Mac — /ebook is recommended for most uses.

How to make a PDF smaller online (free, no install)

Search for “compress PDF free” and use any well-reviewed tool:

1. Upload the PDF.
2. Choose a compression level (usually Low/Medium/High or a DPI slider).
3. Download the compressed file.

Privacy note: Your file is uploaded to a remote server. Do not use online tools for confidential, legal, or financial documents. Use Ghostscript locally for those.

How to make a PDF smaller on iPhone

Method 1: Re-export via Files app

iOS does not have a native PDF compression tool. Workaround:

1. Open the PDF in Files app.
2. Tap the Share button → Print.
3. In the Print preview, pinch-out the first page to expand it.
4. Tap the Share button that appears at the top → Save to Files.

This re-renders the PDF and sometimes produces a smaller file. Results vary.

Method 2: Online tool in Safari

Upload the PDF to a free online PDF compressor in Safari, then save the result to Files. This is the most reliable method on iPhone.

Why is my PDF so large? Common causes

Cause	Size impact	Fix
High-resolution scanned images	Very high	Re-scan at 150 DPI, or use Ghostscript /ebook
Embedded full-size photos	High	Reduce image DPI before inserting
Duplicate embedded fonts	Medium	Use Ghostscript to subset fonts
Unnecessary metadata	Low	Strip metadata with Ghostscript or a PDF optimizer
Uncompressed content streams	Medium	Ghostscript recompresses everything

Scanned PDFs are almost always the largest — a 300 DPI color scan of a single page can be 1–5 MB. Ghostscript with /ebook typically cuts this to 100–300 KB per page.

How much can you compress a PDF?

PDF type	Typical reduction
Scanned color document (300 DPI)	60–80%
Scanned black and white document	40–70%
Text-based PDF (from Word/Docs)	5–20%
PDF with embedded graphics	30–60%
Already compressed PDF	Minimal

Text-only PDFs are already small — compressing them further yields little gain. The biggest wins come from image-heavy or scanned PDFs.

Frequently Asked Questions (FAQ)

What is the difference between “make a PDF smaller” and “compress a PDF”?

They mean the same thing. Both refer to reducing the file size of a PDF — typically by recompressing images inside it, subsetting embedded fonts, and removing redundant data.

Will making a PDF smaller reduce the quality?

For image-heavy PDFs, yes — images are compressed at lower resolution, which may be visible if you zoom in. For text-based PDFs, quality loss is negligible. The /ebook setting in Ghostscript (150 DPI) produces results that look identical to the original on screen and in standard print.

Why is my PDF still large after compressing?

Most likely: (1) the PDF is already compressed and cannot be reduced further; (2) the PDF contains a large number of high-resolution images — try /screen in Ghostscript for maximum compression; (3) the PDF has embedded fonts that account for most of the size — Ghostscript’s font subsetting will help.

How do I make a PDF smaller without losing quality?

“Without any quality loss” is only possible if the PDF has redundant or duplicate data. For image-heavy PDFs, some quality reduction is unavoidable when compressing. The /printer setting (300 DPI) in Ghostscript preserves near-original quality while still reducing file size by removing redundant metadata and recompressing streams.

Can I make a scanned PDF smaller without OCR?

Yes — you are compressing the image itself, not extracting text. Ghostscript or Preview’s Quartz Filter compress the scanned images without running OCR. The PDF remains a scanned image, just at lower resolution.

Related guides

• How to compress a PDF for free — detailed compression guide with all methods
• How to convert a PDF to PNG for free — export as images instead
• PDF to JPG: convert PDF pages to JPEG for free — save as JPEG for even smaller image sizes
• How to extract pages from a PDF for free — remove pages to reduce size
• How to delete pages from a PDF for free — trim unwanted pages before compressing