We just migrated our WP site to a different server and database and none of the internal links to uploaded pdf files had been properly updated (all were still pointing to the development site!)
Not knowing any better, I started going in individually and changing them. I found this plug in and in two minutes it updated 613 links. It saved me HOURS of tedious work. I admit there may have been a better way to do this but I sure didn't know one, so this was a true Godsend.
I am making what I hope is an appropriate support payment/donation immediately.