view pdf in safari lags under new iOS

[scottchu]

I have a html with a <img src='my.pdf'> tag. I use it to view my.pdf only on Safari. my.pdf is converted from a jpg by using some tool (cause I want to bypass a restriction of jpg image of either iOS or Safari). When my iPad is still iOS 3.2, I can move or zoom the image smoothly. But after I upgrade to iOS 4.2.1, moving & zooming become lag. The lag problem also exists in atomic browser, so I think new iOS causes the problem? Does anyone know how to avoid this problem?