We need to know a lot more - What doc? What version of PS? what operating system? Does it open in Acrobat/ Adobe Reader and if yes, in which version?
Also which PDF Version?
Adobe Photoshop Version: 8.0 (8.0x020)
Operating System: Windows XP
Version: 5.1 Service Pack 3
System architecture: Intel CPU Family:6, Model:15, Stepping:6 with MMX, SSE Integer, SSE FP
Processor speed: 1861 MHz
Built-in memory: 2046 MB
Free memory: 1341 MB
Memory available to Photoshop: 1762 MB
Memory used by Photoshop: 50 %
Yes it opens in Adobe Reader 9 Version 9.1.0.
Pdf version 1.3
Sorry pdf version 1.4
I've noticed that in the properties of other pdf documents the 'Application' is Adobe Photoshop but there's no Application programme outlined for the pdf I'm trying to open. Could this have something to do with it?
Photoshop 8 means CS and I may be wrong, but at that time PDF only had language level 1.2 at most. In short: Your PDF is too new and uses features that your old version of PS simply can't interpret. Without upgrading to a more modern version of PS or using alternate tools to rasterize your PDF (export from Inkscape, convert with GhostScript or whatever) I see no way that this wil lever work...