Can't edit a PDF in Acrobat Standard

I'm using Acrobat Std, fully updated. I have a PDF that was created in either Illustrator or InDesign. I don't have access to the original file. When I click on an element to edit it, like an image or text, I get the box with dots on the corners. If I try and click and drag on those dots, nothing happens. I can't move the image or text around. I can flip the image or rotate it.

I've checked the document properties. All security features are set to "Allowed". I can paste an image into the document, but again, I can't move it or resize it, but I can flip it or delete it.

If I create a Word document and save that as a PDF, I have the same issue - I get all the above issue and I can't edit it properly.