Angular/ionic 5 with ng2-pdfjs-viewer. Issues with large pdf files

Question

Currently using ng2-pdfjs-viewer in our ionic 5/angular 8 app with cordova (android app). All pdf files are downloaded into the device and then we use ng2-pdfjs-viewer to show the content. It works fine with small pdfs, but it does not work (no error messages) with files larger than 1.8 mb.

<ng2-pdfjs-viewer *ngIf="pdfSrc" [pdfSrc]="pdfSrc"></ng2-pdfjs-viewer>

this.readFile(this.file.dataDirectory, this.docName)
          .then((data) => {
            this.pdfSrc = data;
          })
          .catch((error) => {
            console.log(error);
          });

...


readFile(path, file) {
    return this.file.readAsDataURL(path, file);
}