Question: Can I copy an individual page or chapter from a sefer for my own use?

Answer: Copying a few pages is usually not a violation of hasagas gevul, since a person who needs only a few pages will generally not buy the sefer. It would seem permissible even according to the opinion that halacha recognizes ownership of intangible intellectual property, since the author often does not intend to prohibit such copying. Although he writes "any portion," his primary intention is to prevent copying significant portions or for commercial use. Especially in libraries, where there are photocopy machines stationed, he abandons hope of such restriction. [One must be careful not to ruin the library's sefer when copying.]

However, to copy a page that has significant inherent value, such as a major summary chart, could be prohibited according the opinion that halacha recognizes ownership.

Certainly, a person who bought a sefer and wants to copy a few pages for his convenience, such as if he is traveling, is allowed to.

In many places, copying individual pages is permitted also according to dina d'malchusa as "fair use."

(Emek Hamishpat, Zechuyos Yotzrim, Intro. 4:1-5; ch. 35:198)