Its oldest version doesn't support

alias) class SimplePdfViewerModule import SimplePdfViewerModule 'SimplePdfViewerModule' does not appear to be an NgModule class.(-996002) simplePdfViewer.module.d.ts(9, 51): This likely means that the library (simple-pdf-viewer) which declares SimplePdfViewerModule has not been processed correctly by ngcc, or is not compatible with Angular Ivy. Check if a newer version of the library is available, and update if so. Also consider checking with the library's authors to see if the library is expected to be compatible with Ivy.