Unable to save PDFdoc object in free version...

Hi, Currently I am using free iOS version of Radaee. When I open a PDF file and create a PDFDoc object

as PDFDoc *mDoc = [PDFDoc alloc]init];
it creates the object but when I try to save this object like
[mDoc save]; or [mDoc canSave]; then It returns 0 instead of 1.
and I unable to edit the PDF file. I try to add annot but it does not let me to do that.

Please help.

Thanks in advance

only a premium license can create and save PDF document.
the demo package actived a premium license bind to package name "com.radaee.PDFView" on ios.