I just upgraded from Adobe acrobat Pro to DC. In the older version, I was able to select multiple text boxes at once, copy them, and past them without any problem. I was also able to select multiple objects that I made (lines, etc), AND text boxes at the same time to copy and paste. Under the older version, I selected multiple text boxes / objects by holding down the Ctrl key and selecting the multiple objects. Now, I seem to only be able to select 1 text box at a time to copy and paste, and even so, I don't seem to be able to select any text boxes with objects at the same time to copy and paste. If I hold the Ctrl key when I try to select multiple text boxes, it only reverts to the most recent text box, and that's it. I am still learning DC and like many of the features that seemed to have improved upon the older versions, but not being able to use the multiple select feature in the newer version is confounding me.
I am still looking for a better solution, but you can copy all the text in a highlighted area regardless of the division between text boxes by clicking the cursor button, highlighting the text, and hitting ctrl/cmd+c. Clicking the cursor button will force you out of the editing tool, so you have to click the edit button again before pasting it into a single text box, but this is the only reliable method I've discovered.
I hope this helps someone else, but please let me know if you find a better way 😊