Compress a PDF to 200 KB

Why a scanned PDF is so big

A PDF from a scanning app is a stack of photos, usually at 300 dpi and high JPEG quality. A single page can be 1 to 3 MB. Portals that store millions of uploads cap certificates and marksheets at 200, 300 or 500 KB, and general-purpose PDF compressors often stop at "medium" without hitting the number you need.

How it gets under 200 KB

Each page is drawn at a resolution, starting at 150 dpi, which is sharp enough to read printed text. The pages are saved as JPEGs, the PDF is rebuilt, and the finished file is measured. The JPEG quality is raised or lowered until the PDF is as good as it can be under 200 KB. If the lowest quality is still too big, the resolution drops to 110 dpi and it tries again, then 90, 72, 60 and 50. The page tells you the resolution and quality it settled on.

Because the whole file is measured, the PDF's own structure is counted too, so the number you see is the number the portal sees. 200 KB is read as 200,000 bytes.

Colour or black & white

Black & white saves pages in grayscale. For a printed certificate, marksheet or ID scan, nothing is lost, and the same 200 KB leaves room for a higher resolution or quality, so small print stays readable. Use Colour when the document has a coloured seal, photo or stamp the reviewer needs to see.

If it already fits

If your PDF is already under the limit, the page says so, and you can upload the original as it is.

Limits

Up to 20 pages, so phones do not run out of memory. Password-protected PDFs need to be opened and saved without the password first. Pages become pictures, so text cannot be selected in the new file.

Have photos instead of a PDF? Drop them here too, or see photos to one PDF under 200 KB.

Reading the result

After the PDF is made, the page shows its size, the number of pages, the resolution in dpi and the JPEG quality as a percentage. 150 dpi with quality above about 30% reads like the original on a phone or laptop screen. If it had to drop to 72 dpi or lower, zoom in on the smallest print before you upload; if it is hard to read, switch to Black & white, which usually buys back resolution, or leave out pages the form does not need.

What the portal checks

Portals check the file type and the byte count, sometimes the number of pages. They do not check how the PDF was made. A PDF whose pages are pictures is what any scanning app produces, so it is accepted wherever a scanned document is.