edit pdf

i have a doc which was done in corral on the website as a pdf.
I want to edit the text. My adobe Acrobat tells me I cant because the font cannot be found. Photoshop just lets me do the first page then gives me an error when i try to open it after i edit the first page. It seems to only do one page at a time.
HOw can I edit this. the original doc is on an old mac.