I think you should make it clear on your ordering page that the Linux version of QCAD Professional is x86. I didn't notice until I'd already paid and started the download . I'm using Debian amd64, for which there are 32 bit compatibility libraries available, but it would be nice if there was a note on the ordering page to say they are necessary.
Edit: After looking through the other forum sections I notice that a few other people have run into this problem. 64 bit Linux has been around for a long time now, so I think it's essential to state on the ordering page that the binaries are 32 bit.