I need to create a pdf with InDesign with a video inside. Exporting the pdf and opening the file it asks me for Flash support. How can you fix it without having to download flash?
Convert the video to a non-Flash format (excluding *.flv and *.swf). Inserting or embedding rich media (non-Flash content) in PDFs will continue to be supported. (i.e., Quicktime, MPEG, 3GPP if if H.264 encoded).
the videos I insert are in mp4, but still asks me to activate the flash
Change your preferences, but note that there's little you can do for other people. I don't recommend trying to use multimedia in a PDF.
Note that even with a non-flash format for the video, whether it will work or not is going to be nothing but a crapshoot.
If you can't control the reader app that will be used, forget it.
Try including a hyperlink in your PDF is a Youtube, or similar, video.