Adobe acrobat X add rectangle

Click the gear icon on top

find the rectangle, click the "->" arrow to add it to the tool bar

in the tool bar click the red rectangle icon

draw a box at where you want to add the rectangle

red click -> property and adjust colors

 

Adobe Acrobat Error No Available System Font when editing text in a PDF file when deleting a character

I was trying to delete an extra period in the end of a paragraph using acrobat X but it said that the font isn't available.

So I followed this link https://helpx.adobe.com/acrobat/kb/error-no-available-system-font.html#:~:text=Acrobat%209,Advanced%20Editing%20%3E%20TouchUp%20Text%20Tool.&text=In%20the%20TouchUp%20Properties%20dialog,current%20font%20you%20are%20using.

although it was not so intuitive.

What I ended up doing was: highlight that extra period I wanted to delete then changed the color to white.