How to convert JPG to PDF: merging, order, size and print layout

When merging ID cards, contracts, invoices or homework into PDF, the usual problems are wrong order, oversized files and print cropping. This article covers order control, page-size choice and size compression.

Format conversion Author tdd8.cn

Combining a few photos into one PDF is one of the most common office tasks: applications, expense claims, submissions. Done well it uploads on the first try; done badly it comes back -- wrong order, text too small, 20 MB that the portal refuses.

1. Order first, merge second

Merge tools usually order pages by the sequence you add the files, not by file name. Rename the images 01.jpg, 02.jpg and drag them in order; that is much easier than reordering pages afterwards. For an ID card, front comes before back.

2. Page size: A4 or "fit the image"

  • A4 portrait: formal documents and anything printed. Images scale proportionally with margins, so nothing gets cut off.
  • Fit the image: the PDF page equals the image size. Fine for on-screen reading, but printing on A4 rescales and may leave large margins or crop.
  • A4 landscape: tables and screenshots; landscape images need a landscape page or they get squashed.

If unsure, choose A4 portrait -- it is the default every recipient accepts.

3. Size: compress the images first

A phone photo is 3-5 MB, five of them exceed 20 MB, and many portals cap at 10 MB. The right order is compress each image to 300-500 KB, then merge:

  • Plain documents (contracts, IDs, invoices): long edge 1600 px, quality 80 is enough to keep every character readable;
  • Detailed material (drawings, handwritten notes): long edge 2000 px, quality 85;
  • Batch it with image compression, then merge with JPG to PDF.

The reverse -- merge then compress the PDF -- re-encodes whole pages and blurs letter edges faster.

4. Three tips for photographing documents

Shoot square on: an angled shot creates keystone distortion, so pages end up different sizes and print crooked. Even light: side light casts shadows that turn into grey patches in the PDF. Leave a margin: include all four corners so later cropping does not eat content.

5. The reverse direction: PDF to images

Sometimes you need the PDF as images (social posts, web previews). PDF to image exports page by page; choose the resolution deliberately: 150 DPI is enough for screen previews, use 300 DPI if you will print or run OCR.

6. Why submissions get rejected

  • The file name contains spaces or symbols and the system fails to parse it -- use letters and digits;
  • Scans are colour and enormous -- greyscale halves the size and often looks sharper;
  • Blank pages slipped into a multi-page PDF -- delete the empty images before merging;
  • Encrypted or read-only PDFs fail on re-upload -- do not submit password-protected files.

FAQ

Can multiple images become one PDF?

Yes, pages follow selection order; rename to 01, 02 first to avoid misordering.

The merged PDF is too big?

Compress each image first, then merge—better than compressing the PDF itself; 1600px long edge suffices for documents.

Can a PDF be turned back into images?

Yes—export JPG per page: 150 DPI for screen preview, 300 DPI for print or OCR.

Tools used in this guide

JPG to PDFImages into a PDF PDF to JPGExport pages as images Image compressionShrink files in bulk
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