Join two pdf files together

I can supply two pdf file attachments which are scans of a single map which is slightly bigget than A3. Note the horizontal crease that runs along the middle.
The task is to rotate one map a quarter turn in one direction and the other map a quarter turn in the other direction and join them together to create one pdf so that all the text is upright. The attachments are too big to add to this site.

So, once bid is accepted, we will send this to the successful bidder.