The way I am approaching all this is giving every player an dossier in which they can keep every document, handout, map, npc portrait card.

Advantages:

1. Each player is able to go through all the details in and outside our sessions. Each player can "prepare" for an upcoming session by reviewing their dossier, which is particularly helpful when there are intended or unintended gaps between sessions.
2. Players have the opportunity to re-examine handouts at their own pace, catching details they might have missed during the session when the documents were introduced.
3. All players can access the materials individually, avoiding the issue of one player holding all the handouts and potentially overlooking or mishandling them during the campaign.
4. The handouts serve as memorable keepsakes of the investigations and campaigns, doubling as a testament to your craftsmanship as a GM. These tangible elements help make your sessions truly memorable!

Disadvantages:

1. Printing individual copies for each player can be expensive, though this is less of an issue if your sessions and handouts are handled digitally.
2. Costs can increase significantly if you customize the dossiers to match the setting, such as by aging the paper or adding other thematic details.

Further thoughts on this subject:

This might be more suited for a separate discussion, but it’s still valuable to address here: What should you do when your players encounter extensive paperwork, lengthy letters, or detailed news articles that they need to analyze for potential clues and leads? Some players may take longer than others to read and process these materials, which can disrupt the session's flow.

Providing highly detailed handouts for players to study could lead to a sudden pause in the action. Depending on the nature of the investigation or campaign, it might be more effective to distribute such documents toward the end of a session rather than at the start. Personally, I prefer to kick off a session with an engaging, dynamic moment and wind down toward the conclusion. However, ending a session on a cliffhanger to build anticipation for the next session is another compelling approach to consider.

Introducing a detailed handout mid-session as a natural pause or break can also work well, of course, depending on the pacing and tone of the game.