Adobe Acrobat is freeware.

Open it in that and then screenshot it [PrtScn] which copies the image of your screen to your clipboard (think that's as a bmp, if not it'll be a jpg).

Open a new document in your graphic programme and use [Ctrl + V] to paste the last thing saved to your clipboard into it.

Then you can save it in whatever format you software allows.

[edit: how big's the file?]