How to split and merge PDFs

Break a big PDF into separate files, or join several PDFs into one, without re-compressing the pages or dropping the document's metadata. Here is the clean way to do both.

These are page operations, not edits

Splitting and merging never touch the content of a page, so they always work (even on scans): the result is byte-for-byte the same pages, metadata carried over.

Merge several PDFs into one

Open the editor and drop in your PDFs.
Turn on Merge into one PDF in the Output panel.
Download the combined file.

Split one PDF into several

Splitting runs from the command line or the free local app:

# one file per page
pdfblah split in.pdf -o parts/ --every 1

# custom groups: pages 1-3 in one file, 4-6 in another
pdfblah split in.pdf -o parts/ --ranges 1-3 4-6

Three ways to do it

Same engine, same result. Pick one:

Online at pdfblah.com: nothing to install, free while we're testing.
On your machine, free and private (nothing is uploaded): pip install pdfblah, then pdfblah gui opens the same tool in your browser.
Command line, for scripts and bulk jobs:

pip install pdfblah

# split into one file per page
pdfblah split in.pdf -o parts/ --every 1

# split into custom groups: pages 1-3 in one file, 4-6 in another
pdfblah split in.pdf -o parts/ --ranges 1-3 4-6

# merge several PDFs, in order, into one
pdfblah combine cover.pdf body.pdf appendix.pdf -o whole.pdf

The app and CLI are open source (MIT). See the pdfblah project on GitHub.

Related page tools

pdfblah can also keep or reorder pages (pdfblah pages in.pdf out.pdf --keep 3,1,2), rotate them (pdfblah rotate in.pdf out.pdf --degrees 90), and crop the page area, all without re-rendering the content.