A Printman's Paper

8 pages per sheet? How many folds?

Paper material cost money, and though it was cheaper than animal skin parchment, printing houses wanted to get the most pages out of every sheet.
So, printmen developed an elaborate scheme for their paper.

One sheet of paper is divided into 4 four leaves.
A1 is the first leaf. Front side is page 1.

The back side of A1 is page 2.
This pattern continues for the three other leaves.

In total, there are 4 leaves and 8 pages.

...Printing intermission...

These pages have been printed and hung to dry. They are now ready for folding

The first fold bends the long side of the sheet in half. Then, a cut is made along the fold.

Each half sheet has 2 leaves and 4 pages.
Again, the long side of each half sheet can be folded and cut.

Here are the 4 leaves and 8 pages, properly cut.

They're ready to be sewn along the marked edge, and perhaps latter bound in a hard cover.