Fix

src/app/modals/document-viewer/document-viewer.module.ts

@@ -0,0 +1,24 @@
+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+import { FormsModule } from '@angular/forms';
+
+import { IonicModule } from '@ionic/angular';
+
+import { DocumentViewerPageRoutingModule } from './document-viewer-routing.module';
+
+import { DocumentViewerPage } from './document-viewer.page';
+import { PdfViewerModule } from 'ng2-pdf-viewer';
+
+
+@NgModule({
+  imports: [
+    CommonModule,
+    FormsModule,
+    IonicModule,
+    DocumentViewerPageRoutingModule,
+    //
+    PdfViewerModule
+  ],
+  declarations: [DocumentViewerPage]
+})
+export class DocumentViewerPageModule {}