Primary suggestion...
A VERY large number of organisations distribute their CAD drawings in PDF format. These drawings contain layers and these layers can flow through to the PDF.
The desktop PDF viewer allows users to turn these layers on and off (very handy, paticularly where the drawing contains lots of detail) but the mobile viewers do not.
It would be very beneficial for mobile users to also have this functionality. It could be argued that with the smaller screens on mobile devices it would be even more beneficial than on the desktop.

Related suggestion 1...
The ability to select multiple layers at a time using a standard windows shift-click would be even more useful. I intend to add this suggestion as a request in for the desktop version.

Related suggestion 2...
AutoCAD has the ability to store different named views of the same drawing with specific layers turned on or off.
If these named views were able to flow through to the PDF file then these PDF drawings potentially become much more useful again.

Currently, even though drawings are created electronically and distributed electronically, largely they still end up being printed on paper. The addition of these features would definitely help people to go fully electronic.

All of these suggestions would apply to to CAD drawings of any type (Mechanical, Structural, Civil, Architectural etc)

I'm trying to edit a PDF on my Android Tablet that I created on my desktop. I spent the $25 to upgrade to DC Pro so that I could edit 5 lines of text on the first page that was created originally on Word, converted to PDF, and then inserted into a larger PDF. It is NOT an image scan. I've edited this text on my desktop.

DC Pro claimed to let me edit documents. When I searched for instructions on how to do prior to subscribing, there were clear instructions on how to do it. I have searched and searched for a solution for this one, basic, simple function.

Such a waste of money. If this is possible, it should be much more intuitive than apparently it is. I'm no ludite! I'm on a business trip and can't alter this text that I need to.

1. Place a signature in a PDF document using Acrobat Reader on iOS (v12.1). Save signed document as PDF_A.


2. Open saved document PDF_A with Acrobat Reader in Windows 10 laptop. Can view the signature.


3. Place another signature in the opened document, save the PDF as PDF_B.


4. Open this PDF_B having two signatures with Acrobat Reader in either iOS or Windows, both signatures are visible.


5. Open same PDF_B with Acrobat Reader in Android (8.1.0, MIUI 10.0.2.0), can only see one signature only which was created in Windows, but not the one created in iOS.


6. Place another signature using Acrobat Reader Android, save it as PDF_C.


7. Open saved PDF_C using Acrobat Reader in Windows and iOS. Now can view only signatures created earlier in Windows, and in Android.


8. Even if use Acrobat Reader Android to open PDF_A, it can't see the signature.


9. If we sign and save a new PDFD using Acrobat Reader Android, use iOS Acrobat Reader to open PDFD, one can see the signature.

Looks like there's a bug in Acrobat Reader Android that makes it unable to view a signature placed in a PDF document using Acrobat Reader iOS.