How to make a PDF smaller
Why PDFs get big and how to shrink one for email or an upload form: Mac Preview, Word, Acrobat, Ghostscript, dropping pages, splitting, and better scans.
A PDF is almost always big because of the images inside it: scanned pages and phone photos stored at far more resolution than a screen or printer needs. Shrinking one means either sending fewer pages or smaller images. Here are seven ways, from the quickest to the most thorough.
What makes a PDF big
| Cause | Typical size | Fix |
|---|---|---|
| A colour scan at 300 to 600 dpi | 1 to 5 MB per page | Downsample images, or rescan |
| A phone photo turned into a page | 2 to 6 MB per page | Resize the photo first |
| Pages you do not need | Whatever they hold | Remove them |
| Fully embedded fonts | 100 KB to several MB | Re-export with font subsetting |
| Repeated edits and incremental saves | Grows each save | Save a fresh copy |
A text document exported from Word or Google Docs is normally small: tens or hundreds of kilobytes. If yours is several megabytes, look for images.
Remove the pages you do not need
The safest size cut is sending less. Cover sheets, blank scanned backs, terms and conditions and instruction pages often make up a large part of a document. Remove Pages from PDF shows every page as a thumbnail, so you can click the ones to drop and download the rest. It runs in your browser, and the pages you keep are copied unchanged, at full quality.
Remove Pages from PDFDelete unwanted pages from a PDF — blank scans, cover sheets, or anything you do not want to share.Remove pages from a PDFSplit it into parts
If the whole document has to go but an email or portal limit is in the way, send it in parts. Split PDF cuts a file every N pages or at the page numbers you choose, and nothing is recompressed. A 40 MB document becomes two 20 MB emails.
Split PDFBreak a long PDF into separate files — every N pages, at chosen page breaks, or one file per page.Split a PDFMac: Preview’s Reduce File Size
- Open the PDF in Preview.
- Choose File > Export.
- Set Quartz Filter to Reduce File Size and save under a new name.
It is fast and free, but aggressive: images can come out noticeably blurry. Check the result before sending.
Word: re-export at minimum size
If you made the PDF from a Word document, export it again: File > Save As, choose PDF, and select Minimum size (publishing online). On a Mac, choose Best for electronic distribution and accessibility. Word can also open an existing PDF and convert it, but complex layouts often come back broken, so use this only for your own documents.
Adobe Acrobat Pro
Acrobat Pro has two options: Compress PDF for one click, and File > Save as Other > Optimized PDF for control over image resolution, fonts and leftover data. The free Acrobat Reader cannot compress. Adobe’s online compressor works too, but it uploads your file.
Ghostscript, for full control
On any computer with Ghostscript installed, one command rewrites a PDF with downsampled images:
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -sOutputFile=smaller.pdf input.pdf/ebook targets about 150 dpi, a good balance for reading on screen. Use /screen (about 72 dpi) for the smallest file, or /printer (300 dpi) to keep print quality.
Make it smaller at the source
The best compression happens before the PDF exists.
- Scan in grayscale or black and white unless colour matters. A grayscale page is roughly a third of the size of a colour one.
- Scan at 150 to 200 dpi for documents. 300 dpi is for printing, and 600 dpi is rarely needed.
- Resize photos before turning them into a PDF. A 12-megapixel photo is far larger than any page needs. Shrink photos with the Image Compressor, then combine them with Images to PDF, which normally embeds JPEGs as they are rather than re-encoding them, so the PDF comes out about the size of the images you put in.
Which method should you use?
- Over an email limit by a little: remove pages you do not need, or split.
- A scanned document for an upload portal capped at 1 or 2 MB: rescan in grayscale at 150 dpi, or downsample with Preview, Acrobat or Ghostscript.
- A report you wrote: re-export from Word or your editor at minimum size.
- A file with sensitive content: use something that works offline or in the browser, rather than uploading it to a compression website.
If the PDF needs a password before you can work on it, start with how to remove a password from a PDF.
Tools used in this guide
Free, and they run in your browser — nothing is uploaded. See every tool on the PDF Tools page.
Frequently asked questions
Why is my PDF so large?
Almost always because of images. A scanned page or phone photo stored at full resolution can be several megabytes on its own, so a 20-page scan easily passes 50 MB. Embedded fonts, duplicated images and repeated incremental saves add more, but they are rarely the main cause.
Does compressing a PDF reduce quality?
Only the images. Compression shrinks large files mainly by lowering image resolution and increasing JPEG compression, which can make photos and fine scans look soft. Text and vector graphics are not affected. Pick a moderate setting and check a page with small print before you send it.
How can I get a PDF under 1 MB or 500 KB?
Start by removing pages that are not needed, then reduce image resolution to about 150 dpi with Preview, Acrobat or Ghostscript's /ebook setting. If a scan is still too big, rescan in grayscale at 150 to 200 dpi. A text-only PDF of a few pages is usually well under 500 KB already.
What is the attachment size limit for email?
Gmail allows attachments up to 25 MB in total per message, and Outlook.com 20 MB. Larger files are sent as cloud links instead. Many government and job portals cap uploads far lower, often at 1 or 2 MB, which is why the scanning settings matter so much.
Can I make a PDF smaller without losing quality?
Partly. Removing unneeded pages, deleting duplicate images and re-saving with object streams shrink a file without touching what is on the page, but they usually save little. Large reductions come from images, so they always trade some image quality for size.