I found the PSoC Creator user manual, but still looking for how to modify thee drawing sheet size.
There is a section "Select Sheet Template" in the PSoC Creator User Guide document.
There is another section "Sheet Template Page Setup" following the section "Select Sheet Template" to describe how to modify the sheet size.
You can also refer the section "Sheet Template Editor" to create your own sheet.
Thank you, Noriaki.
I also found that if you right-click on the schematic sheet outside the schematic outline(frame),
you get the same Select Sheet Template window.