Thanks for the replies. I am part of the University of Portsmouth photographic society and we want to try and sell the photos for charity. Facebook is the only way in which we can reach the clients/other students.
I tried the lightroom slideshow method before I posted on here but it didn't work too well with cropped photos or portrait photos.
With the last batch we posted we put the file name in the description but that took a long time for 400+ pictures. We just wanted a quicker way of doing it.
Watermarking with the file name would be ideal. I couldn't see it in the watermarking tab on the export, is it there or somewhere else?
Are there mac apps that do it? (nobody in the society committee has a windows machine!!)
The print module in Lightroom will let you add the file name or any other data to the print. Then save it as a jpeg rather than print it. You can do a whole group of images at once. The original is not changed, of course.
I do this when I think that people will want to order enlargements. It prints along the bottom, but not on the image.
With watermark factory, the options seem endless, you can save in many formats, ad test, images, save to a different folder or file name, and, of course, insert file names and data. You can put a watermark in as the original file number or the modified file number. I bought mine 10 years ago, and its still working today with windows 7 64 bit.
Here are two samples, one with the file number added to the image in lightroom using the print module, and one using watermark factory.