PDF Glossary: Split, Extract, Merge, Page Range, and More

To split a PDF means to divide one PDF file into two or more separate PDF files. Each output file contains a subset of the pages from the source document. The content of each page — text, images, embedded fonts — is preserved exactly. Splitting is the opposite of merging. Common uses: extracting a chapter, separating scanned batches, isolating pages for separate distribution.

In PDF context, extracting pages means selecting specific pages from a PDF and saving them as a separate file, while leaving the source document intact. Extracting is closely related to splitting — a page range split is a form of extraction. Some tools use the term 'extract pages' to describe the same operation as 'split by page range.'

To merge PDFs means to combine two or more PDF files into one. Merging is the opposite of splitting. The output file contains all pages from all source files, in the order you specify. PDF ME's Merge PDF tool performs this operation locally in your browser.

A page range is a consecutive sequence of pages within a PDF, defined by a start page and an end page. For example, 'pages 5 to 12' is a page range. When splitting by page range, the tool extracts exactly those pages into a separate output file. Page numbers in a page range refer to the PDF's internal page numbering, which may differ from the printed page numbers visible in the document.

The page tree is the internal structure of a PDF file that defines how pages are organized. It is an index that maps page numbers to the content streams, fonts, images, and annotations that make up each page. When a split or merge tool processes a PDF, it reads and rewrites the page tree. Understanding the page tree explains why splitting preserves content integrity: the tool reorganizes the page index, not the content of the pages.

PDF compression reduces the file size of a PDF by optimizing embedded resources — typically images — without re-encoding text or vector graphics. Compression is a separate operation from splitting. After splitting a PDF, you can apply PDF compression to any output file that is larger than needed. Compression does not require re-doing the split.

WebAssembly is a binary instruction format that allows code to run in the browser at near-native speed. PDF ME uses WebAssembly to process PDF operations — including splitting, merging, and compressing — locally on your device. This means your files are not uploaded to an external server; all processing happens in your browser. WebAssembly is supported in all modern browsers.

Flattening a PDF converts interactive elements — form fields, annotations, digital signatures — into static page content. A flattened PDF looks the same but no longer has editable fields. Some PDF operations, including certain split implementations, work more reliably on flattened PDFs. If you encounter problems splitting a PDF that contains form fields or annotations, try flattening it first.