A number of applications are available to help you migrate legacy content to DITA. The degree of success you will experience in using these tools will depend a great deal on the current state of your legacy content. Content that is not already structured will take a great deal more work than content that has already been published as a set of topics, for example an online help system.
One of the more widely used migration packages is Adobe FrameMaker DITA Application Pack, a free plug-in for FrameMaker 7.2, which was released in September 2006.
The Application Pack adds a plug-in to Framemaker that allows editing DITA topics and map in structured view. It is also possible to convert a DITA map (and all the other files it references) into a FrameMaker book. Output can be produced by using the usual Framemaker output processing or by running the Toolkit build process from within FrameMaker.