The simple answer is, no, it's not possible.

There are some possible tricks, though.

The simplest trick is to rotate all of your text by 90 degrees on the first page.  It will still technically be printing in landscape, but, to the end user, it will look like it is portrait.  You can rotate the text in the Format Field dialog.

One issue with the above is that it really will only work with a single record.  You can't have your detail sections march across the page, instead of down it.  But, for your described situation, it should work fine.

It may be possible to also pull this off with subreports.  I've never tried it, so I'm not sure.  But, you may be able to designate a subreport to print in a different direction.  Thinking this through, it could create some really wacky problems if done incorrectly.  So, Crystal may not allow it, on principle.  But, it may be worth a shot, if you need to do something that a simple rotation can't handle.