Images, PDF, audio and video files in MySQL
My recommendation is, as Max has suggested, to store on the filesystem and store a path in the db as varchar.  This has the advantage of not having to deal with the files in the db.  Even on other db's I think storing frequently used binary files in the db is asking for performance issues (storing less frequently used files in the db, OTOH, is a good thing).

However it does have the disadvantage of requiring multiple backups to get all the data your data needs.  A secondary option might be to store the files in the db as a blob (in a separate table) and then store it on the filesystem too.  This way you can just recreate the file from the db if it is missing and you can count on your database to be a complete set of the files for backup purposes.  This may be needless complexity though.

Also if you are storing video files in the db, one real reason to go to PostgreSQL would be the stream-based LOB interface which would allow you to chunk the output.