Adding a pdfs (or documents) library inside the app

Ionic Framework Ionic Angular
1

Hi,
I’m new on Ionic, and I developing an APP with some manuals inside.
I understood that using capacitor I cannot access to the assest folder I already tried with http client (both angular than capacitor)

....
import { Http, HttpResponse } from '@capacitor-community/http';
...
 const readPDF: HttpResponse = await Http.get(
        { url: this.folderPath + 'assets/documents/manuals/handbook.pdf' });
      this.status = readPDF.status.toString();

or

....
import { HttpClient } from '@angular/common/http';
.....
 constructor(private httpA: HttpClient) { }
.....
       const readPDF = await this.httpA.get(
         this.folderPath+'/assets/documents//manuals/handbook.pdf').toPromise();

where in this.folderPath I tried http://localhost http://localhost/public capacitor://localhost and soo on

Is there a best way to add some files inside an APP (both iOS an Android) and givin the access to open them?
We need to give manuals (we have mainly pdfs) to the users

Regards
Marco