In the Multimedia Trust preferences, you can specify whether to play embedded multimedia files in trusted or nontrusted PDF documents. A trusted document is a document that you approved or that was produced by an author you approved. By setting your permissions to play multimedia only in trusted documents, you can prevent programs, macros, and viruses from playing on, and potentially damaging, your computer.

The list of trusted documents and authors is stored internally and can’t be viewed. If you add a certified document to the list, both the document and the author’s certificate are added to the list of trusted documents. All documents that are certified by this author are trusted. (Trusted documents also include PDFs that were created by authors in your list of trusted identities.)

To access these preferences, choose Edit > Preferences (Windows) or Acrobat > Preferences (Mac OS), and then select Multimedia Trust from the left side of the dialog box.

Display Permissions For

Choose whether you want to display security permissions for trusted documents or other (nontrusted) documents.

Allow Multimedia Operations

Select this option to allow media clips to be played. When selected, you can change the permission settings for a particular player and enable options that determine the appearance of the media during playback.

Change Permission Settings For A Player

Select the player in the list, and then choose one of the following options from the menu:

Always

Allows the player to be used without prompting.

Never

Prevents the player from being used.

Prompt

Asks the user whether the player can be used. If you select this option and allow the player to play the media in a particular document, that document becomes trusted.

Clear Your List Of Trusted Documents

Deletes the current list of trusted documents and authors. Use this option to prevent media from playing in documents that were previously trusted documents or created by trusted authors. This option is available only when a PDF that contains multimedia is open.