These can be framed with or without over mounts. Sometimes it is perfectly acceptable to leave the white borders showing so that the titles and the artist's name are displayed when framed. Posters are usually best displayed if they are "dry mounted" onto mount board. This prevents them "cockling" up with temperature change such as exposure to hot and cold walls with radiators turning on and off through the course of the day. Even season change can cause prints to expand and contract and eventually cause cockling during this process if not dry mounted. If you do not want the weight of glass, then your posters can be laminated to protect them in the same way as glass would, such as the example below of Damon Hill.
If you are framing a limited edition print, it is also recommended that you choose conservation or museum quality mount boards to protect the colours of the print.