If the correct title is in the file name and they are standardised, there are options under the "Adding Books" section of calibre's preferences to get the metatdata from the filename rather than the pdf's metadata.
Untick "Read metatdata From file contents rather than file name" and setup a regular expression to match your filenames. If you have trouble with this bit, post an example of your filenames and someone who is actually good with regular expressions will give you a hand