The portal rejected my PDF for being too large. What should I change first?

Reduce the photos before converting, not the PDF afterwards. A modern phone photo is 4–12 MB, and four of those make a file no amount of lossless re-saving will shrink. Resizing each image to around 2000 pixels on its long edge keeps a document perfectly legible at a fraction of the size.

Should I photograph a document or scan it?

Scan it if you have any scanner available, including a phone scanning app — those apps detect page edges, flatten perspective, and clean up lighting, which a plain camera photo does not. A raw photo works, but expect to spend more effort on framing and lighting to get an acceptable result.

Guide

Turning Photos or Scans into a Single PDF for a Submission

Visa applications, rental references, insurance claims, university admissions, expense reports — sooner or later something official demands "one PDF" and all you have is six photos taken on your phone. It's a small task with a surprising number of ways to get it rejected: too large, wrong order, unreadable, or split across several files when the portal accepts exactly one.

Get the capture right first

Everything downstream is easier if the source images are good, and no amount of later processing rescues a bad photo of a document.

Use a scanning app rather than the plain camera if you possibly can. Every phone has one available — often built into the notes or files app — and they do three things a camera doesn't: detect the page edges, correct the perspective so a photo taken at an angle comes out rectangular, and normalise the lighting. The difference between a scanning app's output and a raw photo of the same page is the difference between something that looks submitted and something that looks snapped.

If you are using the camera: shoot in even, indirect light rather than direct overhead light, which casts your own shadow across the page. Hold the phone parallel to the document, not tilted. Fill the frame with the page, leaving a small margin. And check focus before moving on — blurry text is the most common reason a submission gets bounced, and it's invisible on a phone screen at thumbnail size.

Deal with size before converting, not after

This is the step people skip, and it's the one that causes rejections. A photo from a current phone is typically 4–12 MB. Convert four of them and you have a 40 MB PDF, against a portal limit that's frequently 5 or 10 MB.

The instinct is to run the finished PDF through a compressor. That won't help much: the file's bulk is the photographs themselves, and lossless re-saving doesn't touch image data — the reasoning is spelled out in why your PDF is so large. Shrink the images first instead:

Resize each photo so its long edge is around 2,000 pixels. That's roughly 170 DPI across an A4 page — comfortably readable, and a small fraction of the original size.
Save as JPEG at good-but-not-maximum quality. These are photographs, so JPEG is the right format.
Scanning apps often let you export at "medium" quality, which does this for you.

Do this on copies. Keep the originals until the submission is accepted.

Building the PDF

With prepared images, assembling is quick. HerePDF's image to PDF tool takes JPEG, PNG, and WebP, and each image becomes one page:

Drop all the images in at once. Each appears as a row with a thumbnail and filename.
Drag the rows into the order the reviewer should read them. Don't rely on the order they were added — check it explicitly, because this is where submissions go wrong.
Convert, and download the single PDF.

Each page is sized to match its source image, so nothing is cropped or padded. Images are embedded as they are, without re-compression — which is exactly why resizing beforehand matters, since the tool won't quietly shrink anything for you. Everything runs in your browser, so the passport scan or bank statement you're submitting never leaves your device.

A pre-submission checklist

Open the finished PDF and check it as the reviewer will see it, on a full-sized screen rather than your phone:

Is every page the right way up? Fix any that aren't with the rotate tool.
Is all the text legible at 100% zoom — including small print, reference numbers, and signatures?
Are the pages in the order requested? Some portals specify a sequence.
Is every required page present, and no extra page you didn't mean to include?
Is the file under the size limit, and does the filename match any naming convention they asked for?
Is anything cropped at the edges — a page number, a stamp, a signature line?

Two edge cases

They want separate files, not one. Read the instructions before combining. If you've already merged and need to undo it, splitting the pages back out is straightforward.

They want a searchable PDF. Occasionally a submission specifies that text must be selectable, which a photo-based PDF never is. That needs OCR, which HerePDF doesn't do — use a scanning app with a "searchable PDF" option, which handles it at capture time and saves the round trip.