Click or drag a PDF file here
How to Use
Upload Your PDF
Click the upload area above, or drag and drop your PDF file onto the page. Once uploaded, you'll see the file name and original size, so you can decide how much to compress it. Your file stays on your computer — nothing gets uploaded anywhere.
Set Your Target Size
Use the slider or type in a number to set your desired file size. You can pick KB or MB. The slider range automatically adjusts based on your file, and the original size is shown for reference. For example, if you need to email it, you might set it to under 10 MB.
Compress and Download
Hit "Compress" and the tool automatically tests different DPI and JPEG quality combinations to find the sharpest image within your target size. You can expand the log to see detailed information about each step. Once finished, just click to download.
Why Choose PDF Under
Most PDF compressors only let you pick "high / medium / low" quality, and the resulting file size is a mystery. PDF Under is different — you tell it exactly how small you want the file, and it automatically searches for the best DPI and JPEG quality combination to maximize clarity within your target size.
No watermarks, no usage limits, no account required. You can use it as many times as you want without ever hitting a paywall.
For privacy, all processing happens in your browser. Your PDF is never uploaded to any server. Close the tab and everything is gone.
How Does It Work?
The tool re-renders each PDF page as an image, then repackages it as a JPEG-based PDF. JPEG can dramatically reduce file size, but quality drops as compression increases.
The key is finding the sweet spot: the highest DPI (resolution) and best JPEG quality that still keeps the file under your target size. PDF Under runs this search automatically, starting from the highest quality and working down until it finds the combination that just fits.
Common Use Cases
Email attachments too large — Gmail caps at 25 MB, Outlook at 20 MB, and corporate email is often stricter at 10 MB. Set your target size just under the limit and send it. Full guide
Government or school upload limits — Many portals only accept PDFs under 1-5 MB. Set your target slightly below the limit (e.g., 1.8 MB for a 2 MB cap) so you don't have to guess. Government portal guide
Scanned PDFs are huge — Scanners produce high-resolution images for every page. A 20-page scan can easily exceed 50 MB. PDF Under works especially well with scanned documents since they're already image-based. Scanned PDF tips
Large files are slow on phones — Limited memory and processing power means a 30 MB PDF can take seconds to open. Compressed files open faster and scroll more smoothly.
Things to Note
- Text becomes unselectable after compression — Since each page is converted to an image, any selectable text in the original PDF becomes part of the image. If you need to copy text, do it before compressing.
- More pages = longer processing — Each page needs to be rendered and re-encoded. PDFs with many pages (50+) will take noticeably longer.
- Smaller targets mean lower quality — There's no way to fit 300 DPI perfection into 100 KB. But the tool will always find the best quality possible within whatever limit you set.
- Don't set extreme targets — A 50-page PDF compressed to 500 KB means only 10 KB per page, which will look very blurry. As a rule of thumb, 30-100 KB per page gives reasonable results.
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