Exposition Beam: What mnemonesis (see Neural Imprinting) is for, although it’s much more commonly used for imparting knowledge in the data and skillset sense than imprinting knowledge in the history/backstory sense. Nonetheless, it can be done, and as such, tends to be done, at least sometimes – despite the awkwardness that imprinting that sort of information this way tends to come with lots of context and emotional sidebands that you might not want, because copying historical memories this way (rather than distilling them down into a matrix of facts first) means that the recipient remembers them as if they happened to him.
(Abuses of this phenomenon are also well known, and fairly unsubtle. See Mind Rape.)