Adobe's PDF format is by far the most dominant format for distributing documents, especially those containing lots of graphics and images.
However, it's not the easiest of formats to work with and PDF Split and Merge enables you to divide and join separate PDF's to make one big one. The program is not helped by what is both a very dated and awkward-to-use interface, which doesn't actually make the splitting and merging of PDF's particularly easy. You'll spend a good while working out what the various buttons and hierarchical folders do.
Once you've worked out that selecting the right mode on the left menu "Merge", "Split" and "Alternate Mix" is essential, you'll have more hope of progressing. Opening and saving documents is then a case of clicking the buttons until you find the right one. What makes PDF Split and Merge most difficult to use however is the fact that there are no visual previews of what you are doing. If you want to split between a certain page range, then you should be OK. However, if not, you'll end up fumbling in the dark for the right settings.
There are better programs out there for splitting and merging PDF documents than PDF Split and Merge but for those that know exactly which pages they want to remove, it does the job.