Acrobat DC Android doesn't flatten freehand annotations on the PDF, it only flattens ink signatures.
Regarding the availability of "Save As PDF" option, could you please tell us the Android versions on your Note 3 device and Tablet? Also, which Tablet are you seeing this issue on? These details would help us in understanding this difference in behaviour better.
Acrobat DC Mobile Team
Thank you for your response. Samsung Tablet has version 15.2.0 and Samsung Note 3 has version 15.1.
Tablet did the same when it was on version 15.1. Please send me a private mail,
and I’ll send you my document on how to exactly flatten.
Thank you. I have already sent you the mail you requested.
"Save as PDF” option is available in Kitkat printing which is supported in OS versions 4.4 and above. Hence, this option is not available in your tablet having OS version 4.1.2.
Adobe Acrobat Team