You don't turn the Product Backlog into Increments, but the items on the Product Backlog
On pag 7, at the first bullet of the paragraph "The Development Team" the text says "...how to turn Product Backlog into Increments...".
I suggest the word "items" is added to the text. So then it would be "...how to turn Product Backlog items into Increments..."
Paragraph "Product Backlog" teaches us that "The Product Backlog is an ordered list of everything that is known to be needed in the product." So the Product Backlog is a list with items, and the items are turned into the increment. The list itself is not turned into an increment, but remains a list.