how to view border after zooming

I tried to use radaeepdf library 3.1 version.When i try to zoom the pdf file it zoomed the file,then i tried to scroll zoomed pdf to view border parts(When pdf file zoomed all whole pdf is not able to see withing the phone).But it dowsn't show me thos pdf file border parts.It shows the next pdf file.why this happens ?

not sure what your mean.

when first time the pdf open it takes the whole space on the phone screen.there is no any border or margin(free space around the pdf file).when i zoom the pdf files it the borders of pdf not visible.SO i try the see them scrolling,but i am unable to see them .when i try to scroll it moves to next page and i am unable to see parts of pdf files which is not visible due to zoom.

can i have the answer for this ?