What you could do is cut and paste it into an editing program, I generated the product with CorelDraw, and then manually trim away the border with the crop function. That should also take care of the text in the bottom left corner. Doing the same thing again can trim the outside borders of the hex field itself if you need to make the sheets match up precisely.
The last stage would be to save it in a format compatible with Vassal, or export it as a pdf. For latter, if your software doesn't have pdf support, you can get Cute PDF (www.cutepdf.com). I've been using the free version for years, and indeed that is how the sheet was created in the first place.