I guess you may not have Ghostscript installed on your computer. You can get free from here.
http://pages.cs.wisc.edu/~ghost/
However, from my experience, I don't see any difference in quality whether you use ghostscript or not. I usually use non-ghostscript option. So, I would recommend not to bother with 'Ghostscript' unless you need it for another reason (LaTeX for example).
My rules of thumb are as follows.
1) With 2 column articles, I use '2col' option (naturally!)
1-1) If the 2 column articles have tables or figures spanning across columns, I just create another copy of the article in 'landscape' without 'join page' option.
1-2) If the article has such problem only with the abstract page, I just convert the 1 page in 'landscape' as a separate file.
2) With 1 column articles,
2-1) If the fonts are relatively big and/or the margins on the sides are wide, I used 'portrait'. So typical LaTeX documents with wide margin will be good candidates. (e.g,
http://elsa.berkeley.edu/choice2/pre.pdf )
2-2) If the fonts are small or the margins on the sides are narrow, then I use 'landscape'
Overall, other than documents with extremely small fonts and very narrow side margins, the documents are quite readable.
Well, I have the same problem. So I use my rule of thumb 1-1) and 1-2) and create multiple versions of the documents. On the reader, I switch back and forth using 'bookmark' function. (Keep pressing 'bookmark' function will bring up all bookmarks of all the documents on the reader & SD card) I know it is quite inconvenient but at least this way, I do not have to pay extra 400$ to get iliad.
Well, it would be great if it is possible but, judging from the inconsistent quality of PDF files, I guess the conversion should be one by one. Even articles from one vendor (e.g. Proquest) has varying quality. Sometimes articles have clear black border from scanning but not always. In such cases, I had to apply pre-trim option to get it properly converted.
Good luck on reading papers on PRS!