How PDF page ranges work when you split
The page range syntax behind splitting a PDF: single pages, hyphen ranges, comma lists, reversed ranges and how out-of-range numbers are handled.
Reading the page range box
The Pages to export box accepts three building blocks that you can mix freely. A single number picks one page, a hyphen picks a run of pages, and a comma joins several picks into one selection. So 1-3, 5 means pages 1, 2, 3 and 5, while a bare 5 exports only the fifth page. The word all is a shortcut that selects every page in the document, which is what the box starts on. Page numbers are always 1-based, matching what you see in a PDF reader, so there is no counting from zero to trip over.
Ranges are cleaned up before splitting
You do not have to type a range perfectly. If you write it backwards, such as 9-7, it is quietly read as 7 to 9. If your picks overlap, like 1-3, 2, the repeated page is only exported once. The final selection is then sorted into ascending order, so the files always come out low to high no matter how you entered the numbers. This forgiving behaviour means you can jot down pages in any order and still get a tidy, predictable set of files.
Out-of-range and invalid numbers
Any page number larger than the document, or below 1, is dropped rather than causing an error, so 1-3, 99 on a 20-page file just gives you pages 1 to 3. Tokens that are not numbers or ranges are ignored entirely. The one case that stops the split is when nothing you typed lines up with a real page, for example 50-60 on a 20-page file. Then the tool reports that the range does not match any pages and no downloads begin, so you never get an empty file.
One file per page, named by page number
Splitting is not the same as extracting a single combined PDF. Every page in your selection is written out as its own one-page file, copied losslessly from the original with pdf-lib so text, images, size and rotation are preserved. Filenames follow the pattern name-page-N.pdf, where N is the true page number, which keeps them sortable and easy to match back to the source. Because each is a separate download, allow multiple downloads if your browser asks, and expect a brief pause between files so none are lost.