BASALT · JOURNAL
How to split a PDF on a Mac, five ways that actually come up
"Split this PDF" means five different things depending on who is asking. Extracting three pages for a client, breaking a 900-page deposition into chapters, and cutting a file into chunks small enough for an email gateway are unrelated jobs sharing a name. Preview does exactly one of them.
What splitting does to the file
Every output has to be a complete PDF, which means more than copying page objects. Each page references resources: font subsets, image XObjects, color space dictionaries, all in shared object pools. A correct split copies every object a retained page depends on, renumbers them, and writes a new cross-reference table.
It also means deciding about document-level structures. The /Outlines tree holds bookmarks pointing at pages that may not exist in this output, named destinations in /Names are the targets of internal links, and an AcroForm's fields belong to the document rather than the page. A split that ignores these produces files that open fine and fail on use.
The other half of the job is what to leave behind. An output should not inherit the source file's earlier revisions, its incremental update history, or objects no retained page references. If the point of splitting is to send part of a document to someone, carrying unreferenced objects across defeats it, as described in what is hiding inside your PDFs.
Way one: extract specific page ranges
The most common request: pages 12 to 18 as their own file, or pages 1 to 4 and 22 to 30 as two files. Preview handles this. Open the document, show thumbnails, select pages with shift-click or command-click, then File, Export as PDF, and the original is untouched.
Where it stops is repetition. Eleven ranges out of one file means eleven passes through the same dialog, each an opportunity for an off-by-one selection. A tool that takes 1-4, 12-18, 22-30 as one input does it once and identically every time.
Way two: one file per page
Turning a 200-page document into 200 single-page files comes up when each page is its own record: signed acknowledgments, invoices, permit pages filed separately.
Preview cannot do this in one action. Automator can, using its Split PDF action, though naming is limited. On the command line:
qpdf --split-pages=1 source.pdf out.pdfproduces out-01.pdf, out-02.pdf, and so on, zero-padded to the width of the page count. Padding matters, since unpadded names sort page10 before page2 in Finder and in any script that later reads the directory.
Way three: every N pages
Fixed-size chunks are for pipelines, not readers: a scanning bureau wanting batches of 50, a review platform with a per-upload page cap, a printer taking signatures of 16. qpdf --split-pages=50 does this directly. Check the remainder, since a 173-page file split every 50 leaves a final file of 23 pages, correct and occasionally surprising to whatever consumes it.
Way four: at each bookmark or chapter
This is the split manual methods handle worst and that matters most for long documents.
A deposition transcript, a regulatory filing, or a technical manual has an outline, and each top-level entry has a destination that resolves to a page. Splitting there means walking the outline, resolving each destination to a page index, and cutting at those indices, so outputs match the document's own structure rather than an arbitrary count.
By hand that means reading the outline, writing down page numbers, then extracting each range. On a document with forty sections that is forty ranges transcribed by eye, and one transposed digit produces two wrong files rather than one. Reading the destinations the file already contains makes the boundaries exact.
Way five: under a target size in MB
Mail servers reject attachments over a limit and filing portals cap uploads. The requirement is not "split into four" but "no output over 10 MB," which is a different problem.
Size is not proportional to page count. A text page might be a few kilobytes; a 600 dpi color scan might be several megabytes. Splitting a mixed document into equal page counts produces unequal files, so the one you needed under the cap is the one over it.
A size-targeted split has to measure. It accumulates pages, tracking the encoded size of each page's content and its referenced resources, and closes the output before the next page would cross the limit. Shared resources complicate the arithmetic, since a font subset used by fifty pages is stored once in the source but once per output that uses it, which is why an honest implementation measures rather than estimates.
Consider compressing instead, since one file under the cap is easier for the recipient than four. That tradeoff is in compressing a PDF without wrecking the scans.
Frequently asked questions
How do I split a PDF on a Mac for free?
Open the PDF in Preview, choose View then Thumbnails, select pages with shift-click or command-click, then File then Export as PDF to write them as a new document. The original is not modified. Preview cannot split one file into many at once, cut at chapter boundaries, or split under a size limit.
Can Preview split a PDF into separate files?
Preview extracts a selection of pages into one new file but cannot produce many files at once. For one file per page you need Automator's Split PDF action, a command line tool such as qpdf --split-pages=1, or a PDF application with a split feature. Repeating the export per range works but is slow and error-prone.
How do I extract one page from a PDF on a Mac?
Open the file in Preview, show the thumbnail sidebar, click the page you want, then choose File then Export as PDF and save under a new name. You can also drag that thumbnail out to the Finder, which creates a one-page PDF at the drop location. Both leave the source untouched.
How do I split a large PDF into smaller files for email?
Split by target size rather than page count, because a text page and a 600 dpi color scan differ by orders of magnitude, so equal page counts give unequal files. A size-aware split measures each page's encoded content and its referenced resources, closing each output before the limit is crossed. Compressing first is often better.
Can I split a PDF at its chapters or bookmarks?
Yes, if the document has an outline, since each bookmark carries a destination that resolves to a page and those pages are the natural cut points. No built-in Mac tool does this, so it needs an application that reads the /Outlines tree and cuts there. The result matches the document's own structure.
Does splitting a PDF reduce quality?
No. A split copies page content streams and their referenced image and font objects without re-encoding, so output pages are identical in content to the originals. Quality loss only happens if you also compress, a separate operation that downsamples and re-encodes image streams.
Why did the links break in my split PDF?
Internal links usually target named destinations looked up in the document's /Names tree, and a link whose destination page was not included has nothing to resolve to. Bookmarks fail the same way when the outline is copied wholesale rather than filtered to retained pages. A split that rewrites both structures against the kept pages avoids this.
Can I split a PDF without uploading it anywhere?
Yes, and you should. Preview, Automator, qpdf, and native Mac applications all run locally, so nothing leaves your machine. Browser-based splitters transmit the whole document to a server before they can touch it, which for confidential material is a disclosure regardless of stated retention, as set out in what you agree to with cloud PDF tools.
Doing it in Basalt
Basalt splits every N pages, one file per page, by specific page ranges, at each bookmark or chapter, or under a target size in megabytes, from one panel. Every split writes new files and leaves the source untouched. The engine runs in a sealed process with no network entitlement, enforced by macOS at the code-signature level, so nothing is uploaded and there is no account and no telemetry. Splitting sits alongside merging and page organizing among 18 tools in one window. It is $29 once for up to three Macs, with a 24 hour free trial, at basaltformac.com.
Redaction that proves itself
Basalt destroys the content you mark, then re-opens the file it wrote and proves the content is gone before it saves anything. Your documents never leave your Mac.