Compress PDF to 150KB

Who asks you to compress PDF to 150KB? One official example

Government Medical College, Thiruvananthapuram, in Kerala is one example. Its Instructions for uploading documents and photo for MBBS 2026 admission tell students to upload original documents "with size less than 150kB in pdf format" into a shared folder, one document at a time. The list runs to ten items, among them the allotment memo, the SSLC certificate, the Plus Two mark list and the transfer, migration, caste, conduct and medical fitness certificates.

The college's notice also wants the passport-size photo as a JPG of at most 30 KB at 150 × 200 pixels. That is an image job rather than a PDF one, which Compress Image handles. Requirements differ between institutions and years, so go by the notice you received; this page only covers getting a PDF to 150 KB or less.

One document, one file: why a batch works and a merged PDF doesn't

Forms like the one above put the 150 KB limit on each document, and the tool compresses every file in a batch separately against the same target. In a separate batch test, with three files other than the ones in the table, two one-page certificates of 655.0 KB and 655.5 KB came to 105.5 KB and 105.2 KB, and a two-page mark list of 1.32 MB came to 135.9 KB, all three at 150 KB or less with Recommended.

Merging the set first works against you. The college wants one document at a time, and a merged file puts every page under a single 150 KB cap. Merged, those three files would make one four-page PDF; in our page-count test a four-page scan stayed over at Recommended and Smaller (162.3 KB) and fitted only at Smallest (142.6 KB), where its text can no longer be selected. At five pages nothing fitted at any level. Keep each certificate as its own PDF, compress them together in one batch and upload them separately. A single PDF needs no account; batches of up to 20 files need a free one.

How many scanned pages fit in 150 KB?

The table below comes from one test on 2026-11-10: colour A4 test files made like scans at 200 DPI, about 655 KB per page, with the target at 150 KB. There are three compression levels. Recommended and Smaller recompress only the images, so text stays selectable: Recommended starts at 150 DPI, Smaller at 100 DPI, and with a target set both go down as far as 72 DPI. Smallest turns every page into a picture, and handles up to 300 pages at a time on a computer, 60 on a phone or tablet.

With a target set, Recommended already works down through the resolution steps Smaller uses, so Smaller changed the result only for one page (68.7 KB against 104.7 KB, with softer images); from two pages up both gave the same file. Smaller cannot bring in a file Recommended left over: four and five pages were over at both. At Smallest, four pages came to 142.6 KB; five pages stayed over at every level, even as a grayscale scan. In this test, about four pages of colour scan was the limit, and only at Smallest; your own scans will come out differently depending on paper, resolution and photos.

Each figure for a file that fits is where the tool stopped: the first resolution step at 150 KB or less, not the smallest that level can reach. That is why three pages at Smallest (126.7 KB) came out larger than at Recommended (122.3 KB), and why three pages at Recommended came out smaller than two (134.9 KB): the three-page file had to go one resolution step lower.