How to turn photos into a small PDF for uploading
Portals often ask for a single PDF under a size limit, while your documents are photos on a phone. This guide shows how to get from one to the other without unreadable pages.
What makes a PDF of photos large
A PDF made from photos is essentially a container with one image per page. Its size is almost exactly the sum of the images inside it, plus a few kilobytes of structure. A five-page PDF of 3 MB phone photos is therefore around 15 MB. To make the PDF small, you make the images inside it small: fewer pixels and sensible JPEG compression.
Step 1: take clean photos of each page
- Place the page on a dark, plain surface so the edges are easy to see and crop.
- Use daylight or an even light source and hold the phone parallel to the page to avoid a trapezoid shape.
- Turn off flash; it creates a bright spot that hides text.
- Fill the frame with the page, and take one photo per page.
A dedicated scanner app can straighten and whiten pages automatically. Our guide on scanning documents with your phone goes into more detail.
Step 2: crop and straighten
Remove the table, fingers and background around each page with the crop and rotate tool. Cropping alone often cuts a photo's size by a third and makes text appear larger on the PDF page. Rotate sideways photos now, so every page reads the right way up.
Step 3: choose a resolution that stays readable
For an A4 page, an image about 1240 × 1754 pixels is equivalent to 150 DPI, which is comfortable for reading printed text on screen. Around 1000 pixels wide is usually still readable for large print. Going much lower makes small print blurry, which defeats the purpose of the document.
| Pages | Limit | Rough budget per page |
|---|---|---|
| 1 | 100 KB | ~95 KB: fine for one clear page |
| 3 | 300 KB | ~95 KB each |
| 5 | 500 KB | ~95 KB each |
| 10 | 1 MB | ~100 KB each |
Dividing the limit by the number of pages tells you how small each image needs to be.
Step 4: build the PDF and check the size
Add the images to JPG to PDF, put them in order, choose A4 or "image size" pages, and create the PDF. If you have a hard limit, the target-size versions such as JPG to PDF under 100 KB or under 500 KB recompress the images gradually and report the real PDF size.
Then open the PDF and zoom into the smallest text on each page. If it is hard to read, the budget per page is too small: remove unnecessary pages, crop tighter, or ask whether the portal accepts separate files.
Mistakes that make PDFs unreadable or rejected
- Compressing a page to a tiny size when the limit allowed much more.
- Pages in the wrong order or upside down; reviewers may reject the whole upload.
- Password-protecting the PDF; most portals cannot open protected files.
- Uploading a screenshot of a PDF instead of the PDF itself.
Frequently asked questions
How do I make a PDF under 100 KB from a photo?
Crop the photo to the page, keep it around 1000–1240 pixels wide, and use a JPG to PDF tool that targets 100 KB and reports the real size.
Does converting JPG to PDF reduce quality?
Not by itself. A good converter embeds the JPEG unchanged. Quality only drops if the images are recompressed to reach a size limit.
What DPI should a scanned document be?
150 DPI is comfortable for reading on screen and 200–300 DPI is better for printing. Size limits sometimes force about 100–150 DPI.
More guides
- How to extract text from an image (OCR) and get accurate results
- Preparing a document before converting it to PDF
- How to compress an image to an exact size in KB
- Photo and signature size for online application forms: a checklist
- All guides
Paul Digital guides are written from hands-on testing of the tools on this site and are reviewed when platforms or formats change. Requirements set by exam boards, governments and apps vary and change over time, so always check the official instructions for your case. Spotted an error? Email askpaulonline@gmail.com.