Multiple Choice Prompt to Display Different Pages in PDF

Yeah, same things

Use a popup dialog in a document level script to select the language and then simply set navigate to the page number like this:

this.pageNum=101;

The script above will go to page 100 as page numbers are zero-based.  I believe PDF Portfolio navigation to specific documents can only be done by the user interface, not by script.  However, you can use attachments to the main document like a portfolio and create your own navigation system with JavaScript.  There are other methods you could use as well, like creating template pages for the different languages and spawning those templates when the document is opened and the language is selected, or changing layers to the different languages.  Underlined phrases in bold above contain links to articles on each subject.

[Sorry, wrong post]

It's certainly possibly using scripts at document level to trigger on document open.

More complex would be to create a custom dialogue box with language choices (checkboxes or dropdown) when user select language it jumps to that language page. Or something little bit simpler like alert on document open to point user to a dropdown field with language choices where he would select language and then it would jump to that page. Either way you would need a script.