A PDF link is not what most people picture. There is no anchor tag and no href attached to the words — the blue underlined text is simply blue underlined text, and separately there is an invisible rectangle sitting over that area which happens to carry an address. The two have no formal relationship, which explains most of the odd behaviour people run into.
It explains why a link can say “our website” and point at a page that no longer exists. It explains why deleting the words does not delete the link, and why a document can have a clickable area over blank space where something used to be. And it explains why most tools only offer to remove a link and draw a fresh one: editing the address of an existing rectangle is a slightly different operation from creating one, and it is the one people actually need when a company has changed its domain.
So both are here. Click an existing link and its real destination appears — the address, not the text — and changing it leaves the clickable area and the visible words untouched. Draw a box over an area and you can put a new link there, pointing anywhere on the web.
The other useful part is simply showing them. Finding links in a PDF by hovering is miserable, because the target is an invisible rectangle whose bounds you cannot see. A document with eleven links is effectively uncheckable that way, so every link is drawn on the page as a highlighted region with its destination on hover, and a wrong address becomes something you can read rather than discover.
One deliberate limit. The tool will not tell you whether an address still resolves, because checking would mean sending part of your document somewhere to test it. That is a request we would have to make on your behalf without asking, and we would rather list the addresses and let you look.
Free, nothing uploaded, no signup, and your original file untouched.