One of the most used feature of Acrobat Pro is Print-to-PDF function. It's a virtual printer that Acrobat Pro installs on your computer to allow any application to create PDFs. However, Acrobat Pro is expensive especially if you only need the print-to-PDF feature.
CutePDF is a free alternative to Acrobat Pro if you only need print-to-PDF! Best of all, it is completely free for personal and commercial use. It supports both 32bit and 64bit Windows.
Edit: Some more good tools for people looking to avoid Acrobat for whatever reason they choose are
PDF Printing: PDFCreator - provides a lot of functionality for printing pdf documents and allows the merging of documents through a queuing system. It is a very customizable and scriptable PDF printer I have used many times to print batch amounts of pdfs.
Merging PDFs: pdfMerge - provides the same functionality Acrobat Reader professional does for merging pdfs. Allows drag and drop pdfs into a UI and reorganization to merge a bunch of PDF documents with no Acrobat required.