Compress Scanned PDF

Scans are big because every page is a picture. Recommended draws those pictures at 150 DPI: 78 to 93% smaller in our tests, still sharp on screen and on paper.

Free to use
Works on any device
Deleted after processing

Text stays vector-sharp
Sized for email
Every page kept
The original is untouched

PDF

Choose the scanned PDF to shrink

Text stays sharp at every level · your upload is deleted as soon as the smaller file is built

Drag & drop file here

or choose a file from your device

Everything Compress PDF can do

Make a PDF file lighter for email, upload or storage by re-encoding the images inside it, while every page stays. Free, in your browser.

How hard it squeezes

Light: barely touches image quality, so the document stays print-ready
Recommended: clearly smaller, still good on screen and on paper
Strong: the smallest result, made for photo-heavy documents
To a size: 100 KB, 200 KB, 500 KB, 1 MB or a size you type
Only the images inside are resampled

What stays sharp

Text stays vector text, not a picture of text
Fonts stay embedded, so it opens the same everywhere
Line art and diagrams keep their clean edges
Every page kept, and the page count stays the same
Page size, orientation and order all unchanged

The size you end up with

The before and after size, both shown on the result screen
The percentage saved, measured from the two real files
When a size limit cannot be reached, the smallest size it could make, said plainly
Your original file stays exactly as it is on your computer
One compressed PDF to download, named after your document

How it works

Compress a scanned PDF in three steps

Add the scan

Drop the PDF in. Long scans are fine; our 10-page color scans took 12 to 22 seconds.

Recommended is chosen

Strong for the smallest file, Light to keep print resolution, or To a size for an exact limit.

Download

The result shows the new size. Your upload is deleted as soon as it is built.

Step by step

Compress a scanned PDF: a visual walkthrough

A scan going through this page, photographed with our one-page 300 DPI color scan of a letter.

Drop the scan on the box
Any PDF from a scanner, a copier or a scanning app. Long scans are fine; one file at a time.
Recommended suits most scans
Your scan's first page shows beside the levels. Recommended redraws the page pictures at 150 DPI; Light leaves a 300 DPI scan as it is, Strong drops to 72 DPI.
See what it saved
The result compares the scan's size before and after and gives the share saved. Download the smaller copy; your upload is already deleted.

Four scans, three levels

We compressed four of our 300 DPI test scans at each level and opened every result: size, the resolution of the page pictures, and how many pixels visibly changed on page 1 at 100 DPI. Measured on October 22, 2026.

Scan	Original	Light	Recommended	Strong
1-page color scan	1.29 MB	1.29 MB (300 DPI kept)	134 KB (150 DPI)	50 KB (72 DPI)
3-page gray scan	4.53 MB	4.53 MB (300 DPI kept)	429 KB (150 DPI)	158 KB (72 DPI)
1-page scan of a table	1.36 MB	1.36 MB (300 DPI kept)	96 KB (150 DPI)	33 KB (72 DPI)
10-page color scan	12.75 MB	12.75 MB (300 DPI kept)	1.31 MB (150 DPI)	470 KB (72 DPI)

Visible change on page 1: Light and Recommended 0% on every scan; Strong 2.9% on the table scan and 5.3% on the letters. At 5% you can see softer letter edges when zoomed in, but everything can still be read.

Light leaves 300 DPI scans as they are: it is for files that will be printed. The 10-page scan took 11.6 seconds on Recommended and 11.0 on Strong; one-page scans about 2 seconds.

Checked again on 24 October

Two new scans with grainier paper, dropped on this page in a 1366 pixel window and compressed with the button: the 10-page scan as the page opens (Recommended), the 3-page scan on Strong. Each download was opened again and page 1 compared with the original at 100 DPI. Measured on October 24, 2026.

Scan	Original	Level	Result	Visible change	Ready in
10-page color scan, grainy	9.10 MB	Recommended	1.97 MB (78% smaller), 150 DPI	0% of pixels	21.9 s
3-page gray scan, grainy	2.57 MB	Strong	225 KB (91% smaller), 72 DPI	9.7% of pixels	6.6 s

Grain in the paper is detail the compressor has to keep, so these scans saved less than the clean ones above, and Strong changed more pixels: letter edges are visibly softer when you zoom in, though every word still reads.

Why 150 DPI is the sweet spot for scans

Scanners default to 300 DPI because it suits printing and text recognition. On a screen, a full page at 150 DPI already has more pixels than a laptop can show at once, so the extra detail is invisible until you zoom far in. Halving the resolution in each direction leaves a quarter of the pixels, which is where most of the saving comes from.

If you scan often, set the scanner to 150 or 200 DPI, gray rather than color, for letters and forms. Our post Why is my scanned PDF so large? measured what each scanner setting costs.

Before you compress a scan

A few things are best done first:

Turn pages the right way up first: Fix an upside-down scanned PDF.
If you want to search or copy the words, run text recognition (OCR) before Strong: recognition works best on the sharper scan.
Remove blank or duplicate pages: each one costs as much as a page of text in a scan.
Need an exact limit for a portal? Use To a size; it stops at the least loss that fits.

What compression cannot do

It does not clean up a scan: grey backgrounds, shadows and specks are kept, and they cost space. Enhance Scan or Photo whitens the paper and darkens the ink, which also makes the file compress better. A scan has no text layer before or after compressing; OCR adds one.

Frequently asked questions about Compress a scanned PDF

How do I reduce the size of a scanned PDF?

Add it here and press Compress PDF: Recommended is chosen. It redraws the page pictures at 150 DPI, which made our scans 78 to 93% smaller without a visible change on screen.

Will the scan still be readable?

On Recommended, yes, with no visible difference. On Strong the pictures drop to 72 DPI: the letters soften but stay readable, as our letter scans did.

Why is my scanned PDF so large in the first place?

Every page is a photo of the paper, usually at 300 DPI and often in color. One color page can be over a megabyte, so long scans run into tens of megabytes.

Should I scan at a lower resolution instead?

For letters and forms you only need on screen, 150 to 200 DPI in gray is plenty and saves compressing later. Keep 300 DPI for anything that will be printed or read by OCR.

Can I make the scan searchable too?

Yes. Run it through OCR PDF before compressing hard; text recognition is more accurate on the sharper original.

Does it work with very long scans?

Yes. Our 10-page color scans took 12 and 22 seconds. The free plan has a limited allowance of pages and size; Pro removes the limits.

Compress a scanned PDF guides and articles

Working with scansWhy is my scanned PDF so large?A scanned PDF stores page pictures, often with more pixels or colour information than the task needs. Doubling scan resolution roughly quadruples the pixel area. Choose capture settings for the smallest meaningful detail, then measure and inspect the saved PDF rather than treating a DPI setting as a quality guarantee.

Working with scansHow to improve the quality of a scanned PDF before sending itImprove a scanned PDF by fixing orientation and visibility while preserving every required mark and page. Enhancement can improve contrast, but it cannot recover clipped content or detail never captured. Review the saved file at its intended reading size before adding OCR or reducing its size.

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