The essentials
Extract creates a new file with only selected pages. For example, 2-4,7 picks the second, third, fourth and seventh page. Remove does the opposite and keeps the remaining pages in their existing sequence.
Practical steps
Reorder needs every page number exactly once. In a four-page document, typing 4,1,2,3 moves the last page to the front. This changes the page sequence without rewriting the page contents.
What to double-check
Check the page count before and after processing. A table of contents written into the PDF may need manual revision after the order changes.
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