The phrase in the context of paper typically refers to a large sheet of paper that has not yet been cut into smaller finished sizes (e.g., for printing or packaging).
Older archives, such as those from the late 19th century, use "uncut" and "net" in more literal or retail-focused ways. uncut net
In a practical context, "uncut net" refers to the raw material used for DIY insect screens for windows. The phrase in the context of paper typically