How to use the Compress PDF
- Drop your PDF onto the box or click to choose it.
- Pick a level: Balanced suits most documents, Strong gives the smallest files, Light keeps print quality. Custom lets you set the DPI and JPEG quality yourself.
- Click Compress PDF and watch each page being processed.
- Compare the sizes of the results and download the version you prefer. If nothing got smaller, simply keep your original.
Features
- Two methods compared side by side: lossless and image-based
- Exact before and after sizes with the percentage saved
- Never offers a file that is larger than your original
- Presets plus custom DPI and JPEG quality controls
- Optional grayscale conversion for extra savings
- Processed locally: the PDF is never uploaded
Why some PDFs are so large
Most of a PDF’s weight usually comes from images. A scanned contract stores each page as a photo, often at 300 dots per inch (DPI) in full color, and phone scans can be even larger. Documents exported from design software may embed full-resolution photos and several complete fonts. Text and vector drawings, by contrast, take very little space. So the way to shrink a PDF is almost always to reduce the pixels it stores.
How this compressor works, honestly
This tool offers two approaches and shows you the result of each, instead of promising a fixed percentage.
1. Lossless optimization
The file is rewritten with compressed object streams, which packs the document’s internal structure more tightly. Nothing visible changes: text stays selectable, links keep working and images are untouched. The saving is usually modest, from almost nothing to a noticeable chunk for files exported by older software.
2. Image-based compression
Every page is rendered at the resolution you choose and stored as a JPEG image in a new PDF. PDFs store images in many different formats and color spaces, and rendering whole pages is the dependable way to shrink heavy scans and photo-filled documents inside a browser, often dramatically. The trade-off is real: the compressed copy is a set of pictures of your pages, so text becomes part of the image and can no longer be searched, selected or read aloud by screen readers. For text-only documents, it can even make the file bigger, which is why the tool compares sizes and never offers a larger file.
Choosing a level
| Level | Resolution and quality | Best for |
|---|---|---|
| Light | 150 DPI, 80% | Documents you may print |
| Balanced | 110 DPI, 65% | Email, sharing and on-screen reading |
| Strong | 72 DPI, 50% | Strict limits such as “under 1 MB” |
DPI controls how many pixels each inch of the page gets. A US Letter page at 150 DPI is 1275 × 1650 pixels; at 72 DPI it is 612 × 792, about a quarter of the pixels. JPEG quality controls how aggressively those pixels are compressed. Grayscale removes color information, which helps most with scanned text pages that only look black and white.
Worked example
Suppose a 12-page scanned lease is 9.8 MB and a portal accepts 2 MB. Lossless optimization might trim it only slightly, because the weight is in the scans. Balanced compression stores each page at 110 DPI and typically brings such a file well under the limit. If fine print looks soft, try Light; if it is still too big, try Strong or switch on grayscale.
Tips
- Keep the original. Compress a copy for sending and archive the full-quality file.
- Compress last. Merge, rotate and sign first, then compress the final version once.
- If a single page causes the bulk, remove it with Delete PDF Pages or send it separately.
- Need the text later? Use PDF to Text on the original before compressing.
Frequently asked questions
Will compressing make the text in my PDF unselectable?
Only in the image-based copy, which redraws each page as a picture. The lossless optimized copy keeps text selectable, and the table shows both sizes so you can choose.
Why did my PDF not get smaller?
Text-only PDFs are already compact, and turning their pages into images would make them larger. When neither method saves space, the tool tells you to keep the original.
Which compression level should I choose?
Start with Balanced. Use Light if the document will be printed, and Strong or grayscale when you must meet a strict upload limit.
Is my PDF uploaded to a server?
No. Pages are rendered and compressed by your browser on your own device, so the file never leaves it.
Can I compress a password-protected PDF?
No. Encrypted PDFs must be unlocked first in a reader that has the password. After that, the unlocked copy can be compressed here.