Adobe Acrobat Pro
The biggest feature of Acrobat Pro and the reason 90% of people I have seen use it is to combine PDF files. How is this done?
Go to File, Combine, Merge Files into a Single PDF...
Next you may either click Add Files, or you may also click and drag files into the window.
When you have all your files in the window (in the order you want them in the single PDF) go ahead and click Combine Files
Name the new file and there you have it, a single PDF made with multiple PDFs
Another handy feature is the ability to save Word documents as PDF files.
To do this go to "Save as" (in Word) just like you normally would. Where it says "Format" choose PDF.
A good feature when working with companies is the Secure and Sign Feature
The Secure feature lets you password protect your PDF file.
The Sign feature lets you draw your signature or electronically sign the document.