Which links are found
Links that are clickable in the PDF: web addresses, email addresses and phone numbers attached to a page as link annotations. Each is listed with the page it is on, and exact repeats on the same page are collapsed.
Which links are not
A web address that is only typed on the page as plain text is not a link in the file's structure, so it does not appear. Links to other pages inside the document are left out too, because they have no address to list. Other kinds of link, such as script or local-file links, are deliberately dropped.
Handling the list
The links are shown as text rather than as clickable anchors. A PDF can come from anyone, and a tool that opens whatever it finds is not one you want to point at a file you do not trust. Copy the list or download it as a CSV for a spreadsheet.