tjdean is right, the Entourage Edge forums do have a lot about this topic.
1. Someone just posted about a pdf editing tool that allows the pdf to be rotated 90 degrees at the source. Then, it can be viewed in landscape mode, not because the edge supports landscape but because the original pdf has been changed to landscape. The poster also commented that functions like highlighting text still work in this situation.
2. The pdf is simply a graphic form (ie not searchable) however lots of people have posted workarounds to this such as using a tool to convert your Journal notes into something that can be read by Evernote, for example. I don't know specifically if anyone has talked about making the annotations on a text-based pdf searchable, but there are things like table of content entries that can be generated by highlighting text. So some people will highlight text where they want to make an annotation, thereby creating some meta data in the pdf that there is something at that spot. You can then edit the table of content entry to include the keywords you'd probably expect to search for to find that note.
Lots more at
http://www.entourageedge.com/forums/forum.php