You've probably seen "this file is too large to attach" when emailing a scanned document, or a government portal or job application that refuses a PDF over a certain size. Scanned PDFs and anything packed with photos can easily balloon to tens of megabytes. Here's how to shrink a PDF for free, no software to install.
Why PDFs get so big
Most of a PDF's file size comes from the images inside it, not the text. A PDF made by scanning paper, or snapping photos with your phone, is essentially one high-resolution picture per page, so the size adds up fast as pages increase. A text-only document (one saved straight to PDF from Word or a word processor) is usually tiny by comparison.
When you actually need to compress
- Your email provider's attachment limit kicks in (most cap attachments around 20-25MB)
- A government site, job portal, or bid submission system has an upload size limit
- You want to save cloud storage space
How to compress a PDF with Dagochim
- Open the Compress PDF tool.
- Drag your PDF in, or click to choose the file.
- Pick Light, Medium, or Strong. If you're not sure how much you need, use "try all three and compare" to see the results side by side.
- Check the before/after size and a one-page preview on the results screen, then download.
Here's how the three modes differ:
- Light: keeps text exactly as is and only trims hidden junk data plus oversized images (down to 200dpi). Text stays selectable and searchable.
- Medium: keeps text as is and resamples images to 150dpi. This is the sweet spot for email attachments and most form submissions.
- Strong: rebuilds every page as a flattened image. It shrinks the file the most, but you lose selectable/searchable/copyable text and clickable links. Use this only when hitting a strict size limit matters more than keeping the text live.
Alternatives: what Windows and Mac offer
Windows has no built-in way to directly shrink a PDF's file size. Opening the PDF and re-saving through Print > Microsoft Print to PDF sometimes trims a little, but it rarely makes a meaningful difference on image-heavy files.
Mac has a compression option built into the default Preview app. Open the PDF, then go to File > Export > Quartz Filter and choose Reduce File Size. You can't fine-tune how aggressive the compression is, though.
Adobe Acrobat (the paid Pro version) also compresses PDFs, but for casual use a free browser-based tool is more than enough.
Common problems
- It barely shrinks: if your PDF is mostly text with few or no images, it was probably already small, and there isn't much left to squeeze out. Check the "share of the file taken up by images" figure the tool shows you.
- The file needs a password: if it needs a password just to open, unlock it first, then "save as" a new PDF or print it to a new PDF, and compress that copy.
- Editing is locked: Light and Medium may not apply, but Strong usually still works since it rebuilds each page as a flattened image.
Is my data safe?
Yes. Dagochim's PDF compressor never uploads your file to a server — it processes everything inside this browser tab. You can confirm this yourself: if you disconnect from the internet mid-compression, it keeps running.
Before you compress, save a backup
It's worth saving a copy of the original PDF under a different name before you compress, especially if you plan to use Strong mode. Because Strong mode rebuilds the file in a completely different way (turning pages into images), you'll want the original around if you ever need to edit or copy text again later.
You also don't need to compress every single page type the same way. A contract that's pure text probably isn't large to begin with, while a report or portfolio mixed with photos usually shrinks noticeably just with Medium mode. Dagochim shows you the "percentage taken up by images" the moment you upload, so you can get a rough sense of how much it'll shrink without trying all three modes.
If you're starting from a scan
Scanner apps and office multifunction printers often default to 300dpi or higher, but plain text documents are perfectly readable at 150-200dpi. Lowering the resolution at scan time means the PDF is born small, and you may not need to compress it again later. If the file is already scanned, use this guide's compressor afterward instead.
Email, forms, and cloud storage: picking the right mode
If you're attaching a PDF to an email, Medium mode is usually the safest default — it keeps text crisp and searchable while trimming the file enough to clear most attachment limits. For government portals and job application systems that enforce a hard size cap (often somewhere between 5MB and 20MB depending on the service), check the exact limit first, then try Medium, and only drop to Strong if you're still over the limit. If you're archiving a document in cloud storage just to save space and don't expect to edit or search it again, Strong mode is fine since you're optimizing purely for size.
Why not just resize the PDF's pages instead?
It's tempting to think shrinking the page dimensions (making an A4 page physically smaller) would reduce file size, but that's not actually where the size comes from. The images embedded inside the PDF are stored at their own resolution regardless of how large the page appears on screen, so resizing the page itself does almost nothing. That's why compression tools target image resolution and embedded data directly instead of the page size.
Frequently asked questions
Will compressing make the text blurry?
Light and medium modes leave real text alone and only shrink the images, so text never gets blurry. Strong mode flattens every page into a picture, so very small text can look slightly soft if you zoom in a lot.
Can I compress a password-protected PDF?
If the PDF needs a password just to open, unlock it first, save it as a fresh PDF, then upload that copy. If it only has editing restrictions, strong mode usually still works because it rebuilds each page as an image.
Does this work on a phone?
Yes, any modern mobile browser works. For very large files (over 200MB) a computer will be faster and less likely to stall.