Theming
You can theme the PDF viewer and - to a limited extent - also how forms are displayed in a PDF files. However, most PDF documents define how the form is displayed. ngx-extended-pdf-viewer does not overwrite the CSS rules defined by the PDF author.
ngx-extended-pdf-viewer
ships with a light theme and a dark theme. Plus, you can define a custom theme.
Note that there's no theming for forms. Theming only changes the appearance of the PDF viewer. It does not change the way PDF files are rendered.
HTML
<ngx-extended-pdf-viewer
[src]="src"
[theme]="theme"
[backgroundColor]="backgroundColor">
</ngx-extended-pdf-viewer>
TypeScript
export class FormsComponent {
theme = 'light';
}