How to reduce the size of a scanned PDF
Quick answer: A scanned PDF is large because every page is stored as an image. To reduce its size, compress it: Balanced shrinks the page images while keeping the look, and Smallest compresses each page harder for the biggest saving. Scanning in black and white or grayscale and removing blank pages also makes the file much smaller.
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A typed ten-page document might be a few hundred kilobytes. Scan the same ten pages and you can easily end up with a file many times bigger, too large for an email or an upload form. That's not a fault in your scanner; it's what scanning does.
Here's how to shrink a scanned PDF with Quick PDF's Compress tool, how to scan so the file is small from the start, and what to expect from each compression level.
Reduce the size of a scanned PDF with Quick PDF
- Open Compress Go to quickpdfapp.com in any browser, sign in and open Compress.
- Choose your scanned PDF Pick the scan from your Files app, Downloads folder or computer. It's processed on your device in the browser, which matters for scanned IDs, tax papers and medical forms.
- Start with Balanced Balanced shrinks the images inside the PDF, which on a scan is nearly the whole file. It's the recommended level and keeps pages looking clean.
- Compare the size Check the result. Scans usually shrink noticeably, but how much depends on the number of pages and how they were scanned.
- Go to Smallest if you need more For a tighter limit, compress the original again with Smallest. Every page becomes a compressed image. On a scan you lose little, because the pages were images to begin with.
- Save and check readability Download the compressed file, open it and zoom in on small print and signatures. If anything is hard to read, use Balanced or split the document instead.
Why scanned PDFs are so big
When you scan a page, the scanner takes a photo of it. The PDF then holds that photo, not the letters. A full-color photo of a page at high resolution contains a huge number of dots, and each page in the scan is another one.
The biggest factors are:
- Color mode. Color scans are much heavier than grayscale, and grayscale is heavier than black and white.
- Resolution. Higher dpi means more detail and more data. Ordinary paperwork doesn't need archive-level resolution.
- Page count. Every page, including blank backs, adds another image.
For a wider look at what bloats PDFs, see why is my PDF so large.
Balanced vs Smallest for scans
| Balanced | Smallest | |
|---|---|---|
| What it does | Shrinks the images inside the PDF | Rebuilds every page as a compressed image |
| Size saving | Good | Largest |
| Look of the pages | Close to the original | Can soften fine print |
| Any typed text you added | Stays selectable | Becomes part of the image |
On a pure scan the text was never selectable anyway, so Smallest costs you less than it would on a typed document. If you added typed text or a signature on top, that becomes part of the picture too.
Scan smaller from the start
The best way to get a light scanned PDF is to scan it light. If you're using your phone, Quick PDF's Scan to PDF has looks that make a big difference:
- Document: black-and-white cleanup. Great for letters, forms and receipts, and usually the smallest result.
- Grayscale: good when there are pencil marks, stamps or faint print.
- Color+ or Original: only when color matters, such as photos, colored charts or IDs.
Choose Letter or A4 page size if the recipient will print it. Our guide to scanning documents with your phone has more tips on lighting and framing.
Cut pages you don't need
Double-sided scanning often adds a blank page after every sheet. Deleting those can cut a file nearly in half before you compress anything. Use Delete pages to pick and remove them, then compress what's left.
If the document is long and every page matters, split it into parts with Split, compress each part and send them separately.
Reducing a scanned PDF on your phone or computer
Quick PDF works the same way in every browser, so the steps above don't change between devices. A few device notes:
- iPhone and iPad: the Files app's Scan Documents option saves scans as PDFs straight into Files; scans made in the Notes app can be saved to Files as a PDF from the share menu. Open quickpdfapp.com in Safari to compress them. See reducing PDF size on iPhone.
- Android: scans from Google Drive's scanner or a printer app usually sit in Drive or Downloads. Save a copy to the device, then open it in Chrome.
- Office scanners and printers: many save to a computer or email the scan to you. If you can, change the scanner's default from color to grayscale or black and white for paperwork; every future scan will be lighter.
- Mac, Windows and Chromebook: scans are usually in the Downloads or Documents folder. Compress from there and keep the original in place.
What compression can't do for a scan
- It can't make the text searchable or editable. Quick PDF doesn't convert scanned images into real text. To change words on a scan, cover them with White-out and type over them with Add text.
- It can't promise an exact size. Results depend on page count, color and resolution. Check the size after each try.
- It can't restore detail. Compressing an already-compressed scan again mostly makes it blurrier. Always work from the original.
Questions people ask
Why is my scanned PDF so large?
Each page of a scan is a photo, and photos hold far more data than typed text. Color, high resolution and many pages, including blank ones, all make it bigger. Compressing the images and scanning in black and white are the main fixes.
What is the best way to compress a scanned PDF?
Start with Balanced in Quick PDF's Compress tool and check the new size. If you need it smaller, compress the original again with Smallest. Removing blank pages first helps a lot too.
Will compressing a scan make it unreadable?
Balanced usually keeps pages looking close to the original. Smallest compresses harder and can soften very small print. Zoom in on the result, especially numbers and signatures, before you send it.
Can I compress a scanned PDF to 1MB?
Often, if it isn't many pages. Try Balanced, then Smallest, and check the size each time. If it's still over, remove pages or split the file. No tool can promise an exact size for every scan.
Can I make a scanned PDF searchable?
Not with Quick PDF. It doesn't convert scanned images into real text, so the words stay part of the image. You can still add typed text, a signature or highlights on top.
What scan settings make the smallest file?
Black and white (Quick PDF's Document look) is usually the smallest, then grayscale, then color. Skip blank pages and keep the resolution reasonable for paperwork.
Do I have to pay to use Quick PDF?
You can open a PDF and edit, sign or fill it after signing in with Google or email. To download, print or share the finished file you start a subscription with a free trial: 7 days on the yearly plan ($29.78 per year) or 2 days on the monthly plan ($2.99 per month). You are charged when the trial ends unless you cancel, and you can cancel anytime.
Sign in with Google or email and start editing. Saving your file starts a free trial: 7 days on yearly ($29.78/yr) or 2 days on monthly ($2.99/mo). Cancel anytime. 🔒 Your file stays on your device.