This documentation is not using the current rendering mechanism and will be deleted by December 31st, 2020. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
To remove the default css of the extension (responsive css too), add this line to your setup:
If you want to change the size of the images in Magnific Popup, the default size set for popups will be used (definde in constants "styles.content.imgtext.linkWrap.width" and "styles.content.imgtext.linkWrap.height").
If you want to use another size within the pdf viewer, modify
plugin.tx_jhpdfviewer.settings.mfp.width = plugin.tx_jhpdfviewer.settings.mfp.height =
to your needs.