Fix

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

@@ -0,0 +1,17 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+
+import { DocumentViewerPage } from './document-viewer.page';
+
+const routes: Routes = [
+  {
+    path: '',
+    component: DocumentViewerPage
+  }
+];
+
+@NgModule({
+  imports: [RouterModule.forChild(routes)],
+  exports: [RouterModule],
+})
+export class DocumentViewerPageRoutingModule {}