The Radbaz (R. David iBn Zimra, 1479-1589!, Tsfat), cited in Sha'are Teshuva 307:1, discusses whether it is permissible to read a book on Shabbat with the explicit purpose of reviewing its content for editing after Shabbat. At one point, he suggests prohibiting it out of concern that the editor might actually do the revision on Shabbat. He then rejects this approach, since the editor will most likely remember that it is Shabbat by the time he organizes the various accessories needed to write.
Yet, his conclusion is to prohibit it for a different reason: It is considered preparing for mundane needs on Shabbat. He compares it to the prohibition of walking to the city limit on Shabbat, to leave for work immediately after Shabbat. However, it is permissible to read a book for its own sake, and make a mental note of any mistakes discovered for revision after Shabbat.
From this ruling of the Radbaz, Hacham Ovadia (Halichot Olam, Parashat Vayishlach) derives a practical Halacha. There he discusses whether a Rabbi may study sources on Shabbat to collect references needed to write a responsa on Mosa'eh Shabbat. He learns from the Radbaz that there is no concern that the rabbi may inadvertently come to write on Shabbat. He reasons that if in the case of editing, in which the only purpose of reading the book was to make revisions later, there is no concern, then certainly in the case of learning, which is a Misva on Shabbat, and it is not evident that he intends to write responsa after Shabbat, it would be permitted.
SUMMARY
It is prohibited to proofread a book with the intent to make edits on Mosa'eh Shabbat. However, it is permitted to read a book for its own sake and make a mental note of any mistakes discovered for correction after Shabbat.
It is permitted to learn Torah sources on Shabbat to collect sources to write a responsa.
