Which product are you using?
PDF.js Express Plus. (domain: kopjra.com)
PDF.js Express Version
UI version: ‘8.1.0’
Core version: ‘8.1.1’
Detailed description of issue
In mobile when the text field is tapped for text input there is a zoom to that text field. If one tries to zoom out using pinch it does not work, and sends the PDF in the viewer to a strange position and from there even the scroll is kind of lost. The only way to zoom out when in that position is usgin a double tap. This problem is more evident when using Safari on IOS, but it happens in Android with Chrome also.
We would expect the tap to work as it usually does. Thus zooming out the PDF in a controlled way without any jumps to strange position.
Does your issue happen with every document, or just one?
It happens on every document with a form
Here you can see a working integration from pur part: