These videos I came across a year or more ago, but wanted to post them here as they give the true "nuts and bolts" about conserving a work on paper. The clips are made via the Smithsonian and I think they give valuable insight into how any work on paper (broadside, poster or other documents) could be handled, in this kind of situation.
Plus, I personally find them very interesting on a teaching level, but that's just me.
Part 1https://www.youtube.com/v/DeP5KPEcKfYPart 2https://www.youtube.com/v/O0cokmKzwtkEven
Part 3, the encapsulation process, was interesting to watch, since, a poster certainly could be handled this way (it isnt laminated) and is another way to present and display a poster, with it protected from damage or rough handling.
https://www.youtube.com/v/OfzQewjyO6o