I try to use the component and sell the following error:
08:46:28,337 ERROR [com.vaadin.flow.component.internal.ComponentMetaData]
(default task-151)
org.vaadin.alejandro.PdfBrowserViewer has only @HtmlImport annotation(s) which is ignored in Vaadin 14+. This annotation is only useful in compatibility mode. In order to use a Polymer template inside a component in Vaadin 14+, @JsModule annotation should be used. And to use a css file, {@link CssImport} should be used. If you want to be able to use your component in both compatibility mode and normal mode of Vaadin 14+ you need to have @HtmlImport along with @JsModule and/or @CssImport annotations.Go to Vaadin 14 Migration Guide (https://vaadin.com/docs/v14/flow/v14-migration/v14-migration-guide.html#3-convert-polymer-2-to-polymer-3) to see how to migrate templates from Polymer 2 to Polymer 3.