convert to epub questions

[michaelbr]

Greetings everyone:
I'm not sure if this is the correct forum to post this question.

I'm new to eBook/epub, so please bear with me if I made any mistake or asked dumb questions.

I have several ebooks in pdf/lit/doc format and would like to convert to epub, I tried to use Calibre to do it, but sometimes weird char was inserted or formatting is lost. Someone told me not to use convert option but instead to open it in original format and save it in epub format. Can someone tell me what's the best program to do this? Is there any other open source alternative beside Calibre?

Any comments/suggestions is much appreciated.

Thanks
Michael