The fastest way to shrink a PDF depends on what's inside it
A PDF gets large because it contains high-resolution images, embedded fonts, or both. The quickest fix depends on whether you need to keep all that detail. If you're emailing the file or uploading it to a form, you can usually compress it without anyone noticing the difference. If the PDF is a photograph or technical drawing where clarity matters, you have fewer options.
Most people can reduce file size by 30 to 60 percent using free tools that come with Windows or macOS, or by using a free online compressor. Larger reductions — 70 percent or more — usually mean accepting lower image quality or removing pages entirely.
Key Takeaways
- Windows and macOS both have built-in PDF tools that can compress files without installing anything new.
- Online compressors like Smallpdf or ILovePDF work in your browser and delete your file after compression, though you should check their privacy policy before uploading sensitive documents.
- Removing pages, flattening forms, or deleting embedded fonts can shrink a PDF more than compression alone, but these changes are permanent.
- If the PDF contains mostly text, compression has little effect — the real size comes from images, so you may need to re-export the original document at lower resolution.
Using Windows built-in compression
Windows 10 and 11 can compress a PDF through the Print dialog. Open the PDF in any program that can display it — Microsoft Edge, Adobe Reader, or even File Explorer. Press Ctrl+P to open Print, then select Microsoft Print to PDF as the printer. Click More settings or the gear icon, find the option labeled Quality or Print quality, and choose Draft or Economy instead of the default. Print to a new file with a new name.
This method works because it re-encodes the PDF at lower resolution. The result is usually 40 to 50 percent smaller. The trade-off is that text and images become slightly softer, which is invisible at normal reading size but noticeable if you zoom in or print the document.
If the PDF is a form you need to fill out, this approach flattens it — meaning you can no longer edit the form fields. Use this only after you've filled in and saved your answers.
Using macOS built-in compression
On a Mac, open the PDF in Preview (the default app for PDFs). Go to File > Export. In the dialog that opens, click the Quartz Filter dropdown and select Reduce File Size. Save the file with a new name.
Preview's compression is gentler than Windows Print to PDF — it usually reduces size by 20 to 40 percent while keeping image quality closer to the original. If that's not enough, you can repeat the process on the already-compressed file, though each pass degrades quality slightly.
For more control, choose Quartz Filter > Edit Quartz Filters to adjust compression settings manually, but the default "Reduce File Size" option is sufficient for most documents.
Free online compressors for larger reductions
Websites like Smallpdf, ILovePDF, and PDF Compressor let you upload a PDF and read a compressed version without installing software. These tools typically reduce file size by 40 to 70 percent depending on the original content and the compression level you choose.
Upload your file, select a compression level (usually labeled Low, Medium, or High), and read the result. Most of these services delete your file from their servers after a few hours, but read the privacy policy before uploading anything containing personal information like tax returns or medical records. If you're uncomfortable uploading to the internet, stick with Windows or macOS built-in tools.
Online compressors work well for PDFs with many images or photographs. They're less effective on text-heavy documents, where the file size comes from fonts and structure rather than image data.
Removing pages or flattening forms to cut size further
If you only need certain pages from a multi-page PDF, deleting the rest is the most effective way to shrink it. Open the PDF in Adobe Reader (free) or Preview on Mac, select the pages you don't need, and delete them. Save the file with a new name.
If the PDF is a form with fillable fields, flattening it — converting the form fields to plain text — removes the underlying form structure and can save 10 to 20 percent. In Adobe Reader, go to File > Save As Other > Flattened PDF. On Mac Preview, export as PDF and the form will flatten automatically. Do this only after you've filled in all your answers, because you won't be able to edit the fields afterward.
When compression won't help much
If the PDF is mostly text with few or no images, compression has almost no effect. The file size comes from the fonts embedded in the document, not from image data. In this case, you need to go back to the original document — the Word file, the spreadsheet, or whatever created the PDF — and re-export it at a lower quality setting or without embedding all fonts.
If you don't have access to the original file, your only option is to remove pages you don't need. Compression tools won't make a meaningful difference on a text-only PDF.
Comparing your options in one place
| Method | Size Reduction | Effort | Best For |
|---|---|---|---|
| Windows Print to PDF | 40–50% | 2 minutes | PDFs with images; acceptable quality loss |
| macOS Preview export | 20–40% | 2 minutes | PDFs with images; need higher quality |
| Online compressor | 40–70% | 3 minutes | Large files; don't mind uploading |
| Remove pages | Varies | 5 minutes | Multi-page documents; only need some pages |
| Flatten form | 10–20% | 2 minutes | Filled forms; won't edit again |
Frequently Asked Questions
Will compression make my PDF blurry?
Mild compression (20–40 percent reduction) is invisible at normal reading size. Heavy compression (70 percent or more) makes text and images noticeably softer, especially if you zoom in or print the document. Test the compressed version before sending it to someone who needs to read fine details.
Can I compress a PDF that's already been compressed?
Yes, but each compression pass degrades quality a little more. If you compress the same file twice, the second pass usually reduces size by only 5 to 10 percent while making the image quality noticeably worse. Compress once and stop.
What if the PDF is password-protected?
Most compression tools require you to enter the password before they can process the file. If the PDF is locked for editing, you may not be able to remove pages or flatten forms, but compression usually still works.
Does compressing a PDF change the file format?
No. A compressed PDF is still a PDF and opens in any PDF reader. The only change is file size and, depending on the compression level, a slight loss of image quality.
Is it safe to use online PDF compressors with sensitive documents?
Most reputable services (Smallpdf, ILovePDF) delete files after a few hours and use encryption during upload. However, if the document contains tax returns, medical records, or other highly sensitive information, using Windows or macOS built-in tools keeps the file on your computer instead.