PDF File - need to edit a poster for Macmillan Coffee Morning Help!!

[Flowertop]

Hi, need to put some words on a poster that I have found on the Macmillan site to advertise my coffee morning. Have downloaded the poster (A4) and have saved it to my docs. No matter what I do I can't put any text on the poster. Have tried to save in another format but still can't do it. Can someone help me please as I need to get this out asap.
Thanks

ctrl a to highlight all
ctrl c to copy all
ctrl v to paste into word processor
then add your text

You can copy the text into a word processing package, but unless you have Adobe Acrobat software you can't usually edit PDF files as it is a graphical format.

Are you supposed to be able to edit it?

Err you can't edit a PDF document.

You can copy and paste it but you can't edit it.

Whoever sent it to you/designed it will have an editable version I assume?