Why can't I send a video or PDF with MMS?

In order to ensure that your messages are being received and to provide you with the most reliable service across all carriers for sending text messages, .jpg, .gif and .png are the only accepted formats for MMS in Cadence. Formats other than .jpg, .gif and .png are not reliable or widely accepted across carriers and handsets, which can result in messages not being delivered or viewable for all contacts.