- That's really up to you, and it depends on what you want to do with these photos on Facebook. But something around 1200 pixels on the long side is fine for a lot of purposes.
- The export dialog box lets you add watermarks (scroll down) and it also lets you resequence/rename the file names/
- This is all handled by changing the settings in the export dialog box
You don't do this from Slideshow. You do this from the Library Module, you select the desired photos, then you click on the Export button and set the proper settings in the export dialog box.
Thanks for answering I may not have explained myself well.
With the sequence number I need this to appear on front of the photo so that the client can tell me which photo they want.
I used slideshow because I could watermark and put a sequential number on front of the photo. However I do not know how to incorporate reducing the size of the photo as well.
Look into Mogrify, as explained above.