Hi Anna007,
For a table with many columns, I'd suggest using a landscape page layout. Alternatively/additionally, if you insert the linked object as an Excel worksheet, you can re-scale it by clicking on it and using Format|Object|Size. If, when doing that, you uncheck the 'Lock aspect ratio' option, you can scale the object's width and height independently. You can also do much the same by clicking on the object and dragging the vertical/horizontal picture handles.
As for security, you can password protect a Word document, via File|Save As|Tools|General Options. For vba-based proection, check out the Protect Method in the vba help. If you're using links to external Excel worksheets, though, you'd probably want to protect the workbooks too. Otherwise, they could be changed and the changes would then be reflected in your Word document. Again, you can protect a workbook manually or with vba.
Cheers