A hundred kilobytes is one or two pages
Scholarship portals, exam boards and job applications often accept a certificate only as a PDF of 100 KB or less, and a signature or a declaration at 50 KB. At that size the question is not how hard to squeeze the file but what will fit in it at all. This page opens with the answer in front of you: the limit is set, grey pages are on, the resolution ceiling is 150 DPI — enough to read small print on A4 — and the planner measures your own photos and says how many pages will fit before anything is written.
A worked example from our own test set: a 2400 × 1800 desk photo of a dense typed page and one colour photo. The planner read “about 70 KB a page in colour, 64 KB in grey: 1 page fits” — and saving the two pages to 100 KB took the solver several passes, lowering only the heavier page, to land at 99,946 bytes. The same dense page alone weighed 37 KB at 72 DPI and 102 KB at 150 DPI, which is why a third page would not have fitted.
What to switch on, in order
- Document mode, for legibility. On the Photos step, “Treat this photo as a document” squares the page up and whitens the paper, so what does fit is easy to read. It does not make the file smaller on its own: on our dense test page it made the page heavier at the same resolution (146 KB against 102 KB at 150 DPI), because the page now fills the sheet and the ink is sharper. Pair it with the ceiling below.
- Grey. Already on here. On a page that is already nearly grey it saves little (about 5 % on our test page); on a colourful certificate it saves more, and costs nothing in legibility.
- The ceiling. 150 DPI is the floor for small print on A4. Going to 72 DPI makes the file smaller and the text noticeably soft; the builder lets you, and tells you the DPI each page ends up at.
- Fewer pages per file. If the portal takes several files, the Save step can write one PDF per photo, each under the limit.
What it will not do
It will not write a file that meets the number and cannot be read. Below a quality floor the builder stops and states the closest size it reached. It also cannot promise that a portal will accept the file — only that the file is under the size it reports, at the page size and resolution it reports. For limits from 200 KB up, use JPG to PDF under 200 KB or the size-limited builder, and what fits in 100 KB has the figures behind all of this.
Questions about JPG to PDF under 100 KB
Can a PDF under 100 KB still be read?
Yes, for one or two pages of a document. How many depends on how dense the page is: our densest typed test page weighed 102 KB at 150 DPI and 37 KB at 72 DPI, so one fits at 150 and two or three at 72. The planner on this page measures your own photos before you save, rather than writing an unreadable file to hit the number.
How do I get under 50 KB?
Press 50 KB on the Quality step. One page in grey at a lowered resolution is the realistic ceiling. If the closest the builder reaches is above 50 KB, it says so and names what is left to try: a lower ceiling (72 DPI is screen quality), a tighter crop, or fewer pages.
Are my photos uploaded?
No. The file is written, measured and rewritten until it fits, all inside this tab. Your photos are never sent anywhere, and nothing is spent from a metered data plan.
What does the PDF contain?
Your pages as images, in grey unless you switch colour back on: no text layer, no file names, no camera or location data, and no title unless you type one. The receipt after saving lists the measured size against the limit you set.
The portal also has a minimum, like 10 KB. Does that matter?
Type it into the At least field. A file that comes out under the minimum is written again with more detail until it is inside the range, and the receipt says it was.