This map looks really very small and should not be difficult to convert into a custom map. I would like to stress that such a trivial thing as a few rectangles are probably more suited to the more "normal" way where you end up with a .img file for the garmin.
We are going to end up with a .kmz file that GoogleEarth uses, and place it in the "\Grmin\Custom Maps" directory on the unit (or on its memory card, if you have one).
So, step one is to convert it to an image. For this I will use a free graphics manipulation tool called imagemagick. I use this to convert and manipulate the images (for example, to convert from UTC to Lat/Lon I run it through a distortion using imagimagick). For your .pdf, I suspect all we will need to do is convert it to a .jpg.
After playing with a few options, here is the command I used:
convert +antialias -colorspace sRGB -density 200 .\Landscape.pdf map200.jpg
I determined that the provided PDF seems to be an image that is already antialiased, so I turned off antialiasing (I know, that + makes it look like I'm trying to add it).
I played with various DPI settings and found 200 to be "adequate". Going up to 300 didn't help any - this pdf is not a terribly high quality image.
I'm attaching the resulting file.