Saud, when you run iSilo, did you check Menu->Options->Display ?
Entry 'Font': Select the desired size of displayed text. The number of listed font sizes is system dependent. iSilo can interpret the font selection in one of two ways:
'Relative': Text displays in a size relative to the selected font, so you can select a larger font to make all text relatively larger or select a smaller font to make all text relatively smaller.
'Absolute': All text displays in the selected font regardless of the font sizes specified in the document.
Hope that helps
Alex