Hi,
You can resize the table by resizing the container first. Set the container very wide and then adjust the column widths.
For setting the page to A4 do the following: create a blak page and set it settings to A4. Then click insert page from the ribbon (insert tab). Click the little arrow below insert page and choose page template. Now from the taskpane have a look at the bottom where you will see the options create template from current page. Give it a name, something like A4Printing. If you check the checkbox which says use this template for all pages in this section you will get the same setup with every page you create.
There are some limitations between the client and the web app. The client offers more functionality than the app version.
hth