You can download the free, 30-day trial version of Premiere Pro here.
The trial version of Premiere Pro CS5 and earlier had a major shortcoming: It lacked many of the most useful and popular codecs, including codecs for MPEG-2, AVCHD, and RED media. This meant that people had a hard time evaluating the software for real-world use.
The trial version of the current version of Premiere Pro includes all of the codecs that are included with the full version of Premiere Pro. This means that you can import and export to all of the supported file formats using the trial version.
See this page for more details about the trial version.
For lists of formats that you can import into and export from Adobe Premiere Pro, see these pages: