KB article ID:2800
Adobe's Form Wizard tool can turn your word-processor-generated PDF into a form. Note that this tool is only in the full version of Adobe Acrobat (not the free Reader version).
The exact process for running the Form Wizard depends on what version of Acrobat you're using, but some tips on how to ensure that the wizard's conversion will be successful, are below and at http://blogs.adobe.com/loridefurio/files/loridefurio/DesigningForms-UE.pdf (starting on p.3).
Checkboxes can be made using one of these: □ (Unicode Character 'WHITE SQUARE'). These will let the user check as many as they want.
Radio buttons can be made from one of these: ○ (Unicode character 'WHITE CIRCLE'). If you want a form on which you can select only one option, put a group label above them, like this:
Hair color
○ Blonde
○ Brown
Fill-in-the-blank fields must have labels to the left of, or under the underscores. So the following won't work:
Name Date of Birth
_______________________ ____________