How do I get rid of the purple arrow while editing a PDF file on Mac?

I am using a MacBook Air and I don't have Adobe for reading PDFs. When I open a PDF using Preview and I use the drop down arrow on the title of the PDF to rename it, a very annoying purple arrow flashes incessantly and stops me typing a new name. How do I make it stop and how do I make it go away?

What it it for and what is it trying to do?

[Re-Titled by Moderator]