Many job applications and online submissions ask for all documents as one PDF file, but you usually have an ID copy, certificates and a form as separate files. Here’s how to combine them, get the pages in the right order and keep the size within the limit.
In short
- Open Merge PDF and choose or drop all the files.
- Use Move up / Move down to put them in order; Add files if you forgot one.
- Merge and download the single file.
- To rotate or remove pages, continue in Organize PDF.
- If it’s too big, use Compress PDF.
Why systems want one PDF
PDF is the ISO 32000 standard, which the PDF Association describes as a way to exchange and view documents independently of the software or device used to create, view or print them. Pages look the same everywhere, which is why application systems like it.
Real requirements from Thailand:
- National Children’s Day awards 2570 (2027) (childrenday.moe.go.th): merge all documents into one PDF file of at most 50 MB.
- A Uttaradit Rajabhat University job announcement published on the OCSC website: attach all documents as one PDF file when applying by e-mail.
- The Court of Justice e-Filing manual for lawyers: attachments must be .pdf files of at most 5 MB each (a 2019 manual; check the latest version).
Before merging, read the announcement for the file type, number of files and size it allows.
Merging, step by step
- Open Merge PDF.
- Choose or drop the files, up to 200 MB each.
- Order them with Move up / Move down to match what the announcement asks, e.g. form, ID copy, certificates.
- Merge and download; the originals on your device aren’t changed.
Files are never uploaded; merging happens in your browser, which suits documents with personal data such as ID copies.
Reorder, rotate and delete pages
If a page is upside down or a blank page slipped in, Organize PDF does it all in one place:
- preview every page before saving;
- move pages, rotate left or right, and delete pages;
- download a new file; the original isn’t touched.
To split some pages out into another file, see Split PDF.
Too big after merging
- Use Compress PDF, especially for scanned or photographed pages.
- Delete pages the announcement doesn’t ask for.
- If you scan yourself, pick a moderate resolution rather than the highest.
On a Mac with Preview
Apple’s instructions: open the PDFs, choose View > Thumbnails, drag page thumbnails from one PDF into the sidebar of the other, and drag thumbnails to reorder. Apple warns that Preview saves changes automatically, so choose File > Duplicate before combining.
Note
This article is based on the PDF Association, the National Children’s Day system, a job announcement on the OCSC website, the Court of Justice e-Filing manual and Apple Support, read on 30 September 2026. Each system’s rules can change; follow its latest announcement.
