The phrase "separate booklet" refers to a small book that is detached or not attached to the main book or document. It is usually used to provide additional information or details that are related to the main content. Full definition
Later, the kids were asked to point to the «sprock,» which was shown in a separate booklet among other unfamiliar objects. (sciencenews.org)
The Psoriasis Program consists of 13 separate booklets (more than 600 pages) and will give you the best natural medicine treatment options. (thepsoriasisprogram.com)
Furthermore the planner came with a separate booklet for contact details (of fellow bloggers, people I have worked with and people whom I've met on events) and another yearly overview which I used to record birthdays of blogger friends. (clothesandcamera.com)