wojciechm,
If you just resize the page, it will not automatically resize the objects on it, you will have to change them manually.
If you wanted, however, at the creation time of your objects, you could use the variables ¤t.pagewidth and ¤t.pageheigth as part of the object's width and height, and use some math to calculate a value proportional to the page's size.
For example, if you create a box, and use this for it's width and height:
Width: =(¤t.pagewidth / 2)
Height: =(¤t.pageheight / 2)
It will create a box with a size that is half your page's size. Then, if you make your page 11x17, it will enlarge the box proportionally.
Of course, this has to be done at the time that you're creating the objects, and you have to design your entire form around this. Also, it will make the object unmovable and unscalable using the mouse, so you will have to manually enter the coordinates where you want your box to be. I would recommend that you place the box at the appropriate place before using such code.
You may or may not actually need or want to do this, but I thought I'd mention it, since it's related, and if you're going to dynamically change the page size in your current project, this may be something you'd be interested to know.
Regards,
Raphaël Lalonde Lefebvre