Is there an easy way to post an old site, including updating media file links?

We’ve hit a major hiccup in our workflow, as we’ve gone behind another development company who did a terrible job. They’ve imported HTML on pages (there are over 400 pages), which is fine, as most are very old archives, but the links for every PDF for each publication issue is linked to the old site, not media files within WordPress’s directory. I’m not sure why the last company did not do any of this, but it’s our issue now.

Is there a relatively easy way to streamline this and have the links updated somehow, maybe match the file names and update the links? What I mean is, is there a way to upload all the media files from the old site and have the links on individual pages updated in an automated fashion? Again, there are over 400 pages, each of which have several PDF links.

I was wondering if there was a way to target the PDFs by file name matching and remove the first part of the link and replace it with the right file in the media directory.

Any ideas? Any plugins out there that might do the job? I’m not a scripting genius by any means, nor can I consider myself a back-end programmer, so the easiest solution, the better.