If you need support from Yola please contact us via firstname.lastname@example.org or make use of our live chat service! We are working on a new approach to community-based support and during this transition period we are not adding any new threads to this forum. Many thanks to everyone who has participated over the years and we look forward to unveiling a new peer-to-peer support system soon!
In the sitebuilder, click 'File Manager', from there you can upload your files to your site. They won't be in the format you mentioned however (hello123.yolasite.com/data.doc), it'll be "hello123.yolasite.com/resources/data.doc".
As to providing a download link, you can do this using Yola's 'File Widget'. Once you've selected a file using that, it'll place an icon, file name, file size and file type on your page!