i have built an app, it basically displays manuals for my work, i have taken pdf's and converted them into JPG files, so they display fine, but i need to set it that when each image in pressed on it either pops up in a window that allows pinch zoom or goes to a separate page that allows the user to zoom in wth possibly double tap and pinch zoom, but mainly pinch zoom, as the manuals have some text and can be tricky to read on a small device screen.
Any reason you didn't leave them as PDFs and use a PDF viewer? I know there are some that work as plugins, and also a JS PDF renderer.
Depending on how your app is structured, you might be able to get away with just modifying the viewport meta tag for the page, since you can specify initial, minimum, and maximum zoom levels. A Google search should be able to get you several options.
OTH, if you're using a framework, or building a SPA (single page app), then you may need to invest in a gesture library and some additional support code. You might try looking at Hammerjs to detect pinch zoom gestures.