What do I need to do this?
Nothing special. Just add all the files you want to merge in the Combine Files dialog and Acrobat will automatically convert all non-PDFs to PDFs and then merge them.
What is the software package I need to purchase?
For example, yes. Note that there are two "tracks" you can use: A subscription (paid monthly or yearly), or a "perpetual" license with a one-time payment. Generally speaking, the former is a better option.
Thanks for the help!