Flex has no inherent functionality to do doc conversions. You
are also looking for the ability to convert several different file
types that might require seperate conversion methods. Also, it is
important to note that Flex does not have very good HTMl
functionality. In fact, it has a very limited subsed of HTML tags
that are allowable and also require some distinct formatting
requirements. So, if you are trying to convert PDF's and Docs, RTF
etc, you might have a difficult time trying to get them to diosplay
in the Flex RTE.
I have struggled with trying to get a good PDF converter for
multiple file types. Adobe does have some good server side
utilities, but budget might be an issue.
You can find several PDF converters that are server based
that you migth be able to leverage.
If you are CF user, Scorpio does have a better integration
with PDF and LiveCycle services that may help when it is released.