Up to 3 attachments can be added to a post. Maximum file size is 1.5MB. The following file extensions are currently allowed:
3ds, bm, bmp, dcl, doc, dst, dwf, dwfx, dwg, dxf, env, gif, gz, gzip, htm, html, iam, idw, ipn, ipt, jfif, jpe, jpeg, jpg, log, lsp, pdf, png, png, psd, rfa, rvt, svf, text, tif, tiff, txt, vcf, xls, xml, zip
zip can always be used both to reduce file size and include other file types.
In addition, images can be embedded in a post using the Insert/Edt image option in the post editor toolbar
Sr. Web Product Manager
Autodesk Knowledge Network