How to select pages in existing pdf to new PDF?

Hello,

   I am new to Adobe Acrobat and I would like to seek your help and expertise on creating new pdf document from my existing pdf document.

    I have an existing pdf document of over 4000 pages. I need to select page 1 to 100 of my existing pdf document  and to create a new pdf document called my_new_document from those page 1 to 100 pages of my document. My College Professor suggest suggest i use snpping tol to copy each page of the document and paste them into pdf. I would like to ask you if you , the experts may suggest an easy way for me to do it since I hear adobe is powerful than sipping tool that I don't have to manually copy each of the page from 1 to 100 pages which is alot of manual copy!

Thank you so much,

Du