PDF6 min read
How to Compress a PDF: Pick the Right Method for Your File
A scan, a Word export and a photo brochure all shrink in different ways. Find out what makes your PDF heavy and the best way to make it smaller on any device.
How to compress a PDF depends on what is inside it. Scans and photos shrink a lot when their resolution is lowered, while a text PDF exported from Word is already small and barely changes. A free online compressor such as FileKiwi handles the image part on any device, and Windows, Mac, iPhone and Android each have a few options of their own.
Why PDF files get so big
A PDF is a container. It can hold text, fonts, vector drawings and images, and each of those takes space in a very different way.
- Images. A phone photo or a color scan holds millions of pixels per page. The same page as typed text needs a few kilobytes.
- Full size pictures. When you place a large photo in a document and make it small on the page, many apps still store every original pixel in the PDF.
- Embedded fonts. Fonts travel inside the file so it looks the same everywhere. They add some size, usually far less than images.
- Extra pages. Blank backs of scanned sheets, duplicates and long appendices all add weight.
A quick test tells you which kind of PDF you have. Open it and try to select a single word. If you can, it is a text PDF; if the whole page gets selected like a photo, or nothing happens, it is a scan.
Color matters too. A color scan of a black and white letter stores color information for every pixel, so it is much heavier than the same page in grayscale, with no benefit to the reader.
Make PDF files smaller while text stays sharp. Free, no signup.
How to compress a PDF by document type
The same compressor gives very different results on different files. Match the method to the document in front of you.
| Document type | How to recognize it | What makes it smaller | FileKiwi level |
|---|---|---|---|
| Text PDF from Word, Google Docs or an invoice system | Every word can be selected, few pictures | Little to gain; shrink pictures in the source file, remove pages | Recommended, expect small savings |
| Scan or phone photo of paper | Text cannot be selected, page looks like a photo | Lower resolution, grayscale, tighter crop, fewer pages | Recommended for email, Strong for upload limits |
| Photo heavy PDF (catalog, portfolio, menu, brochure) | Large color photos on most pages | Lower image resolution | Recommended for screens, Light for print |
| Slides exported from PowerPoint, Keynote or Google Slides | Landscape pages with backgrounds and screenshots | Compress pictures in the deck before export | Recommended |
Text PDFs from Word or Google Docs
If a text PDF is several megabytes, the cause is almost always a few large pictures, such as a logo saved as a huge photo. Shrink those pictures in the original document and export again. That beats compressing the finished PDF, because the text and layout stay untouched.
Scanned documents
Scans give the biggest savings, because every page is one large image. Recommended (about 150 DPI) keeps normal print readable; Strong (about 72 DPI) is for strict upload limits, so zoom in on small print before you send it. If you can rescan, choose grayscale for plain text pages, or turn a color file gray with Black and White PDF, which often trims the size a little.
Photo heavy PDFs and slides
Brochures, portfolios and slide decks look best when you keep some image detail. Use Recommended for files people will read on a screen and Light for anything that goes to a printer. With slides, compressing the pictures inside the presentation app before you export usually gives a cleaner result.
Compress a PDF online with FileKiwi
This works the same in Edge, Chrome, Safari or Firefox, on a computer or a phone.
- Open Compress PDF.
- Add one or more PDFs. Each file can be up to 100 MB.
- Pick a level: Strong (about 72 DPI), Recommended (about 150 DPI) or Light (about 300 DPI).
- Download the result. FileKiwi shows the new size, the old size and the percentage saved.
If you are not sure which level to choose, start with Recommended. If the file is still too big, run the original again with Strong; if a photo, stamp or signature looks soft, go back to Light. Your original file is not changed, so you can try all three.
Compression runs on the FileKiwi server with Ghostscript. Typed text stays sharp and selectable, because mainly the images are reduced. If the new file would not be smaller at all, FileKiwi keeps your original and tells you.
A copy of each PDF you add is kept in a private folder on the server for 30 days, then deleted; the compressed result is not stored. When a form names an exact limit, such as 200 KB, read how to compress a PDF for online forms, which covers target sizes in detail.
How to compress a PDF on Windows 11
Windows 11 has no built in PDF compressor. Printing the file again with Microsoft Print to PDF does not reliably make it smaller.
If you still have the Word file
- Click a picture in the document, open the Picture Format tab (Format under Picture Tools in older versions) and choose Compress Pictures.
- Clear Apply only to this picture so every picture is included, pick a lower resolution and click OK.
- Choose File > Save a Copy (or Save As), select Browse, pick PDF in the file type list and click Save.
If you only have the PDF
Use a browser tool. Open FileKiwi in Edge or Chrome and follow the steps above; nothing has to be installed, which also helps on work and school PCs.
How to compress a PDF on a Mac
Preview can shrink a PDF without extra apps. Open the file, choose File > Export, pick Reduce File Size in the Quartz Filter menu and click Save. On macOS Tahoe 26 the Export window also offers Optimize images for screen and Save images as JPEG.
The filter uses fixed settings. It often makes photos and scans look blurry, and you cannot choose how strong it is, so open the result and zoom in before you send it. When the quality is not good enough, the browser method with Recommended or Light gives you more control.
How to compress a PDF on iPhone and Android
iPhone
iOS 26 brought the Preview app to iPhone. Open the PDF in Preview, tap the menu next to the file name, tap Export, choose PDF and move the slider to change the file size, as described in Apple's Preview guide. On any iOS version you can also open FileKiwi in Safari and pick the file from the Files app.
For new documents, a good scan is the best start. Our guide on how to scan documents on iPhone shows how to crop tightly so the file starts out smaller.
Android
Android has no standard built in PDF compressor, and options vary by phone brand. When you scan with the Google Drive app, use Crop & Rotate to cut away the table around the paper and Filter to switch to grayscale. For an existing PDF, open FileKiwi in Chrome and choose the file from Downloads or Google Drive.
Can you compress a PDF without losing quality?
Partly. Some changes lose nothing at all, and some lose detail you may not notice on a screen.
- No loss: remove pages nobody needs with Delete PDF Pages, and export again from the source file after shrinking its pictures.
- Almost no visible loss: the Light level keeps images at about 300 DPI, which is print quality for most documents.
- Visible loss when you zoom: Recommended and Strong lower image detail. Text stays sharp, but photos and scanned pages get softer.
Avoid compressing the same file again and again. Each pass that lowers image quality adds more blur, so always start from the original.
Which method to pick
- Scanned document for email: FileKiwi Recommended, then check the small print.
- Strict upload limit: Strong, or a size preset, and send only the pages the form asks for.
- Text PDF that is oddly large: shrink the pictures in the source file and export again.
- Mac without internet: Preview with Reduce File Size, if the result still looks good.
- Brochure that will be printed: Light, so photos keep their detail.
Keep the original file until you have opened the compressed one and checked every page.
FAQ
How do I compress a PDF for free?
Open the FileKiwi Compress PDF tool in any browser, add your file, choose Strong, Recommended or Light and download the smaller version. It works on Windows, Mac, iPhone and Android without signup. On a Mac you can also use Preview with the Reduce File Size Quartz filter, and on iPhone with iOS 26 the Preview app can export a smaller PDF.
Why did my PDF barely get smaller?
It is probably a text PDF, or it was already compressed before. Text and fonts take very little space, so there is little to remove. If a text PDF is still large, a few big pictures inside it are the cause; shrink them in the original document and export the PDF again.
How do I compress a scanned PDF?
Scanned pages are images, so lowering their resolution gives big savings. Use the Recommended level for email and Strong for strict upload limits, then zoom in to check that small print is readable. Removing blank pages and converting a color scan to grayscale makes the file smaller still.
Can I compress a PDF without losing quality?
Removing pages and exporting again from a cleaned up source file lose nothing. The Light level keeps images at about 300 DPI, which looks the same as the original for most printed documents. Stronger levels lower image detail, while typed text stays sharp at every level.
How do I make a PDF smaller on my phone?
On iPhone with iOS 26, open the PDF in the Preview app, tap Export, choose PDF and move the file size slider. On any iPhone or Android phone you can open FileKiwi in Safari or Chrome, pick the PDF from Files, Downloads or Google Drive, compress it and save the smaller copy.
Try Compress PDF now
Make PDF files smaller while text stays sharp. Works in your browser, free and without a watermark.
Open Compress PDF