JoshHancock,
Do you have the original files for this PDF? Meaning, were you the one that created it? It sounds to me that it was saved as a file format that isn't PDF and then someone changed the file extension
EXAMPLE...
The file was originally named filename.jpg. Someone then went into the folder where the file is located and renamed it to filename.pdf.
Is it possible that this happened? If so, you will need to revert it back to its original name (filename.jpg). You can then edit it in Photoshop and save it as filename.pdf. Let me know if this does not make sense.
Reply: Only I have touched this file, it has just been on my laptop, and began as a PDF then it has stayed as one. It was never a jpeg, so I think one of the layers I added (say an image from google) was corrupt and caused the file to be inaccesible.. could that happen?