How do I enable saving of filled-in fields on a PDF form?

Question

Some PDF forms can be saved, including all filled-in field data:

Some others can not be saved, and all filled-in field data are lost:

Answer 1

If you are using Adobe Acrobat X to make the form, set all the fields as you want them, then click File, Save As, Reader Extended PDF, Enable Additional Features. The resulting PDF form can be saved when filled in, if opened in versions of Adobe Reader before XI.