Why is my scanned PDF so big when it only has text?

Because a scanner saves each page as a photograph, not as text. The size depends on the image resolution and colour, not on how many words are on the page.

What DPI should I use to scan documents for online forms?

Around 150 DPI in greyscale is enough for most typed certificates and keeps files small. Use higher DPI only if the document has very small print or the notice asks for it.

Will compressing a PDF make the text unselectable?

With our tool, yes. Each page is turned into an image, so text cannot be selected or searched afterwards. Keep your original file if you need the text.

How do I get a 5-page PDF under 200 KB?

Aim for about 190 KB total, which is roughly 38 to 40 KB per page. Greyscale pages at about 1000 to 1240 pixels wide with medium quality usually fit that budget.

Is my document uploaded to your server when I compress it?

No. The compression runs inside your browser on your own device, and the file never leaves it.

How to compress a scanned PDF without making it unreadable

Updated 11 October 2026

Compress PDF to any size →

You scan five pages of mark sheets, the PDF comes out at 4 MB, and the exam portal says maximum 200 KB. This is the most common upload problem on Indian recruitment and admission forms. The good news is that a scanned PDF can almost always be brought under the limit while staying readable, once you understand why it is big in the first place.

Why a scanned PDF is so large

A PDF made in Word or downloaded from DigiLocker stores text: letters, font names and positions. A page of text like that can be just a few kilobytes. A scanned PDF is different. Each page is a photograph of paper, wrapped inside a PDF. The file size is decided by the image, not by how many words are on the page.

An A4 page scanned at 300 DPI is about 2480 × 3508 pixels, which is nearly 8.7 million pixels. In full colour, even with JPEG compression, that page can easily weigh 500 KB to 1 MB. Phone scanner apps often save at similar or higher resolution. Five such pages and you are at 4 MB before you know it.

The three settings that matter

1. Resolution (DPI)

DPI tells you how many pixels are used for each inch of paper. For printed text on a form upload, 300 DPI is far more than an officer needs to read it on screen. Around 150 DPI (roughly 1240 pixels wide for A4) keeps normal printed text sharp, and even 100 to 120 DPI is usually readable for typed certificates. Halving the DPI cuts the pixel count to a quarter, which is the single biggest saving. See pixels, cm and DPI explained for the arithmetic.

2. Colour or greyscale

Colour pages carry three channels of information. Most certificates, mark sheets and ID proofs are perfectly readable in greyscale, and greyscale pages compress noticeably smaller. Keep colour only if the notice asks for it, or if a coloured stamp or photo on the document must be visible.

3. JPEG quality

Each page image is stored with lossy compression. Lower quality means smaller pages, but too low and you get blurry blocks around letters. For text pages, a medium quality setting is usually the sweet spot. Read lossy vs lossless compression if you want the detail.

Worked example: 5 pages, 4 MB, limit 200 KB

Suppose a form wants your graduation mark sheets as one PDF, maximum 200 KB, and your scan is 5 pages totalling 4 MB.

Set a budget with a margin. Aim for about 190 KB, not exactly 200 KB, because the PDF wrapper adds a little overhead and some portals count 1 KB as 1000 bytes. See KB and MB explained.
Divide by pages. 190 KB ÷ 5 pages = 38 KB, so roughly 40 KB per page.
Pick settings that fit 40 KB. A greyscale A4 page at about 1000 to 1240 pixels wide, at medium JPEG quality, usually lands in the 30 to 70 KB range for a typed document. Dense pages with tables and stamps sit at the higher end.
Check, then adjust. If the result is 230 KB, lower the quality one step or reduce the width slightly. If it is 120 KB, you have room to raise quality for sharper text.
Zoom in before uploading. Open the output at 100% and read the roll number, name, marks and seal. If you cannot read them comfortably, neither can the verifying officer.

Setting	Approx. size per A4 page	Readable?
Colour, 300 DPI, high quality	600 KB to 1 MB	Excellent, but far too big
Greyscale, 150 DPI, medium quality	60 to 120 KB	Very good
Greyscale, about 110 DPI, medium-low quality	30 to 60 KB	Good for typed text
Greyscale, 72 DPI, low quality	Under 25 KB	Small print often illegible

These are typical figures, not guarantees: a page full of tiny print, a coloured background or a creased scan will be bigger than a clean white page.

The trade-off: pages become images

Our Compress PDF tool works by redrawing each page as an image at the size you choose and building a new PDF from those images. That is what makes big reductions possible for scans, and it all happens in your browser, so your documents are never uploaded anywhere.

The cost is that every page in the output is a picture. If your original PDF had selectable text (for example a DigiLocker certificate or a form you typed), that text will no longer be selectable or searchable after compression. For uploads that a person will look at, this does not matter. If you need searchable text, keep the original as well, and only compress the copy you upload.

For a text-based PDF that is already small, do not compress at all. Re-rendering a 90 KB DigiLocker PDF as images can actually make it bigger.

Tips that save more than any setting

Crop the margins. Remove the table surface and black borders around the page before making the PDF. Every pixel of background costs bytes.
Scan flat and well lit. Shadows and grey paper texture compress badly. A clean white background compresses very well. Our guide on scanning documents with your phone covers this.
Upload only the pages asked for. If the notice wants the final-year mark sheet, do not attach all six semesters.
Use a preset. For fixed limits, try compress PDF to 200 KB, 100 KB or 500 KB.

Questions people ask

Why is my scanned PDF so big when it only has text?: Because a scanner saves each page as a photograph, not as text. The size depends on the image resolution and colour, not on how many words are on the page.
What DPI should I use to scan documents for online forms?: Around 150 DPI in greyscale is enough for most typed certificates and keeps files small. Use higher DPI only if the document has very small print or the notice asks for it.
Will compressing a PDF make the text unselectable?: With our tool, yes. Each page is turned into an image, so text cannot be selected or searched afterwards. Keep your original file if you need the text.
How do I get a 5-page PDF under 200 KB?: Aim for about 190 KB total, which is roughly 38 to 40 KB per page. Greyscale pages at about 1000 to 1240 pixels wide with medium quality usually fit that budget.
Is my document uploaded to your server when I compress it?: No. The compression runs inside your browser on your own device, and the file never leaves it.