This is a great tool with a nice, user-friendly interface.
Note: PDF-XChange Viewer is discotinued and replaced PDF-XChange Editor (linked to this page).
PDF-XChange Editor includes all the necessary tools to work on a PDF file: it allows you to create, view, edit, annotate, OCR and digitally sign PDF files. With this software you can create PDF files from scanned documents, images, text files, and Markdown files, among others. It offers over a hundred features and has a user-friendly interface. There is also an Enhanced OCR plugin as an optional extra.
This is a shareware version of the software - you have to pay in order to use some of the features. The full version can be bought on the publisher's website with prices starting at €37.