Two-way PDF converter?

Documents are part of our everyday lives. We make, read, print or send them to people every now and then.

When I was in college, we were required to make reports in PDF formats, that way the documents are read-only and cannot be altered by any other person.

I was surprised when I saw a software that can convert pdf to word because I only know of word to pdf conversions.

It also isn't too expensive and can be used for two years with full technical support. I wonder if I would need one in the future. At least, I can always check this pdf software again.