There are 2 different things going on with pdf's. some have trext in them, and you can just cut/paste the text, so you can paste to the forum, or notepad, or ms word easily.
The others, the ones that are scans of catalogs, and have not been through OCR, are just pictures, you can't quite as easily cut/paste them like text, but you can nevertheless cut and paste them. In reader cut as a rectangle after zooming in where you want , (you have to cut only at a picture when there are pictures and text mixed on some pdf's , don't ask why, it's wicked evil and messy computer magic ;P)
You can then paste directly into irfanview and save as jpg afterwards, don't need word/paint etc...