You can copy text from apdf file with the Acrobat reader, just select the text cursor tool and drag/select the text you want to copy and paste it in any word processor.
If you want to paste texte into an Acrpobat file you neeed to have the full version, and even with the full version it is not very easy.
Acrobat is not a text EDITOR!
This great software has been designed so every computer with every system, Mac, Wondows, Unix, Linux etc. can show the exact text/illustration keeping intact the layout of the designer.
It is a one way vector of communication and it does very well.
So useful i.e. for advertising agency to send thru Internet to clients, layaouts of brochures, books ads for approval. They don't have to edit, just comment or approve…
It safely embed any exotic font so you can print it with any printer…
It is a real jewel when used for what it has been designed for…
As any file that you can send thru internet, some stupid ones may embed viruses or whatever they want so ti is spreaded in your computer when opened, Adobe is working hard every day to find new solutions to protect our computers (mostly Windows).