Allow landscape pages in PDF files in email subscriptions

**What problem will this feature request solve?**
Currently the dashboard PDF are attached to emails having all pages in portrait view only which is not suitable for dashboard with full width mode on
**Describe the solution you'd like.**
A clear and concise description of what you want to happen.
Add an option to chose the PDF pages orientation
**How does this feature request impact you?**
For example, is it a minor inconvenience, or does it block important work?
Just another step of improvement
**Additional information**
Add any other context or screenshots about the feature request here.

The issue names no files or tests, so begin by locating the dashboard PDF generation and email-subscription entry points and tracing where portrait orientation is fixed. Clarify how the orientation option should apply to dashboard pages, then verify that emailed PDFs support both portrait and landscape output.

Written by the indexing model from the issue text.