Personally, I always use ftp to put things on a webserver with my ISP. And I never have seen any message about 'not valid doc file' from ftp (and moreover I'm sure it doesn't ever give such an error message).
I'm afraid this MS Office forum will not be able to help you with Acrobat. However, as it is a paid product, you should be able to get support from Adobe.
When I am trying to upload my word 2003 file in the net it is showing warning message that it is not valid doc file. I tried the same in several site & found the same error. Not sure why it is happening.
I installed Acrobat 5.0 to convert those docs as pdf but in word no option is showing for convertion. When I tried with diinstaller then it is showing following error.
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