Multiple lines in a fillable PDF

I have made and successfully saved a fillable PDF.  I can open it and type in it, but it is in a paragraph form and I can't get the cursor to go from one line to the next.  When I get to the end of line the print just gets smaller.  The cursor does not go to the next line.  I have to click in the next line in order for the cursor to go there.  Since this is not the normal way you type a paragraph, it is rather inconvenient in my document.  How can I get the cursor to go to the next line automatically when typing the paragraph?