I'd like to make a stage size with A4(300dpi).
2480 x 3508 px
If then I cannot see the proper size in flash player.
So I'm planning to make a reduction of stage like "248 x 350" / 90% contraction view.
How can I implement this job?
If I understand the question correctly
You can create a 248 by 350 swf stage and use scaleX and scaleY properties of your A4 content (which can have actual size of 2480 by 3508) to zoom in/out.
Here is a small demo