Have a trial version, am not able to save a document after I've made changes. Why is that?

[#1]

Have a trial version, am not able to save a document after I've made changes.  Why is that?

[#2]

Hi,

if you use Adobe Reader to view your PDFs you cannot save any changes by default.

To do this you need at least Adobe Acrobat to add additional Rights (aka Usage Rights aka Reader Extensions) to your PDF.