Preparing a .pdf for DrivThruRPG's print-on-demand

I've been encouraged to provide a print version of Soth. So I'm starting to investigate what that would involve.

In this initial phase, I only have three one concern:

• Will my current .pdf layout work for the print version? Are my margins wide enough? (Answered, below)
• How do I create a cover? (Answered, below)
• What will happen to my page numbers (which are currently on the outside corners)

I'm also aware that there's tonnes of other stuff I don't know that I don't know.

After looking at DriveThru's 'Publish' section, I've found a checklist that hopefully covers all these unknown unknowns: Print checklist (.pdf). Here are some other concerns I have after reading that:

• Do I need a barcode? (Answered, below)
• What is 'bleed'? And do I need it?
• Are my page numbers evenly-divisible? (Answered, below)
• What does "Last page removed for use by LS" mean?

One of the things that baffled me in that checklist was the acronym 'LS'. This seems to stand for 'Lightning Source', based on this tutorial video (not embeddable) I've also found at DriveThru.

So I'll need to download a cover template from LS. Heading over to the site, it gives me a choice between 'Independent Publishers' (using a service called 'Ingram Spark') and 'Medium to Large Publishers', using LS. So, I have two more questions:

• Do I need to set up an account with Lightning Source, and then link that to my DriveThruRPG account?
• Am I in the 'Medium to Large' category, because I'm with DriveThruRPG?
• (After I've done that) Where is the cover template?

Things I've answered, so far

• Looking at my Scribus file, it looks like my margins are fine.
• LS should have a template I can use for my cover.
• Even if my page numbers aren't evenly-divisible, it should be easy enough to change that.
• DriveThru has another printing checklist that says "We do not include barcodes."