Adobe Acrobat Pro DC - Can't Select Multiple Objects?

[Thai Mac]

I don't know what I'm doing wrong, but in the latest version of Adobe Acrobat Pro DC, for the life of me when I'm editing the PDF there's just no way to select multiple objects. Ctrl+Shift doesn't work, and I can't draw a box to select multiple objects. What am I doing wrong? Please help. Thanks.

[Bernd Alheit]

Try the forum for Adobe Acrobat.