From our posting on our old blog site last September (because we keep being asked about this issue!):
Many people ask us whether it is possible to include audio and/or video files (e.g. .mp3 and .mp4 files) as part of a PDF – or even 3D models. The simple answer is that these are enabled as features of Adobe’s product range, with players for such files (and others) provided within the standard readers. The Adobe reader feature list is very impressive:
For onward distribution of these PDFs this can result in difficulties however. Embedding media files can result in PDFs that are very large and thus cumbersome to distribute. Furthermore, the target user’s reader must be able to process the embedded information – typically this will be fine as long as the end user has a version of the Adobe reader that is sufficiently up-to-date. Finally, restrictions may apply in some corporate environments that specify what may, or may not be embedded in a PDF file.
Assuming none of these issues presents a problem for a particular application then the Adobe option is the one to use, based on no issues of confidentiality or copyright, and no need to amend/update the file or media.
Where any of the above conditions do not apply, alternative approaches are available. The most important step is to separate the media files from the PDF itself, using linking rather than embedding. In this case the media files are simply invoked by clicking on a link or image in the PDF. The files themselves may be located almost anywhere, but typically will be hosted on a web server. Assuming standard cross-platform file formats, such as .mp3 and .mp4 are used, the user’s device will play the linked file in a separate player window (or in the background for audio content on some devices), whilst continuing to display the active PDF page. The major advantage here is that the PDF can be kept small, is easy to distribute, and will work on every technology platform that supports standard PDF viewing. It overcomes the updating issue also, since the central files can be updated without the need to amend the end user’s document.
Where copyright protection is required, the PDFs with linked multimedia can readily be made secure using the Adobe or Drumlin digital rights management (DRM) systems for example, and then be distributed securely. An example of the latter we have handled recently is an academic text that relies on a large number of audio files to enrich and clarify the text. The files have been placed in folders on Dropbox and the links applied throughout the text, wherever required. The end result is a copyright-protected PDF which is less than a Mbyte in size, with linked audio clips amounting to some hundreds of MBytes. The latter are accessed as and when required by the readers, and may be updated and augmented as and when required.