how to do both download pdf in browser and will go to other page When someone submits the form

What Sanford said 🙂

In addition, while this isn't really what you are asking, it seems like the most elegant way to do this is to have the thank you page be the page you get to after the form submit, and then email them with the PDF link. This has the added bonus of verifying email addresses for you...if they want the PDF, they have to give you a legitimate email address.

You're getting a bit ahead of yourself. 🙂

Forcing download, regardless of document type, is a distinct goal — and one that you can't meet in all browsers in Marketo. (It will not work in any version of Internet Explorer.)  So you'd need to be able to do this across-the-board first to then combine it with the idea of having a redirect to a Thank You page after/during the download.

To roughly approximate what you're describing, you can open a separate window in browsers that don't support direct download (I posted code for this years ago) and hope for the best. But remember, when a browser absolutely insists on handling a MIME type locally, for example Chrome's PDF Viewer, you can't force your way around that. You have to wait for it to be opened in the local viewer and then click a Download icon. The .DOC in your example should be fine however.