It's possible for users to complete most PDF forms in Adobe Reader, but when user's try to save the changes they get a popup prompting them that the PDF cannot be saved and would need to upgrade to Adobe Acrobat to have this functionality.
Since Acrobat 7 (or possibly) 8 it's possible to create a form so that it can be completed and saved in reader. In Acrobat open your PDF, and select Advanced -> Enable usage right in reader from the menu. This will prompt you to save the form and then anyone using Adobe reader can complete it.
Once that's done you can open the form in ColdFusion, populate some of the fields and serve it up to the user. Once they fill it in, save it and get it back in ColdFusion you can read the contents using the PDF related tags.
Please note: It's currently not possible to set the "enable usage rights in reader" flag from ColdFusion, you need a copy of Adobe Acrobat or access to Adobe LifeCycle server to do this.