If you are receiving an error like this when you want to show your file on the screen. "Error: unsafe value used in a resource URL context" then you need to sanitize your resource url. here is a pipe that you can use for this purpose.

safe.pipe.ts

import { Pipe, PipeTransform } from '@angular/core';
import {
  DomSanitizer,
  SafeHtml,
  SafeStyle,
  SafeScript,
  SafeUrl,
  SafeResourceUrl
} from '@angular/platform-browser';

@Pipe({
  name: 'safe'
})
export class SafePipe implements PipeTransform {
  constructor(protected sanitizer: DomSanitizer) {}

  public transform(
    value: any,
    type: string
  ): SafeHtml | SafeStyle | SafeScript | SafeUrl | SafeResourceUrl {
    switch (type) {
      case 'html':
        return this.sanitizer.bypassSecurityTrustHtml(value);
      case 'style':
        return this.sanitizer.bypassSecurityTrustStyle(value);
      case 'script':
        return this.sanitizer.bypassSecurityTrustScript(value);
      case 'url':
        return this.sanitizer.bypassSecurityTrustUrl(value);
      case 'resourceUrl':
        return this.sanitizer.bypassSecurityTrustResourceUrl(value);
      default:
        throw new Error(`Invalid safe type specified: ${type}`);
    }
  }
}

view-document.component.html

<iframe [src]="document.file_url | safe: 'resourceUrl'"></iframe>