Better ways to search large PDF files?

I have a several thousand page text book in pdf format which is indexed DT pro office. Is there any utility (i.e. faster search, better results with boolean operators) to saving the book as chapters of 10-20 pages in length vs leaving as complete book?
Thanks in advance.

Splitting the PDF into smaller chunks would improved the utility of searches and See Also, especially if the book covers a number of identifiable topics.

I hate to break up my own documents for that purpose. An alternative would be to create notes for each of the important topics in the book, linking each note to one or more page links. As those notes will be searchable, a search for any of the topics would find the note, and the page link(s) in the note would quickly take one to the important page(s) within the book.

thanks for the input. I did break the book into chapters, but also kept a copy of the original complete text. Breaking it up did improve searches. This book happened to be in pdf format. Do you know if devonthink can index other types of ebooks with DRM such as kindle, epub, etc?