Signals Notebook: PDF Export fails for Parallel Experiments with a large number of subexperiments

Description: When attempting to export a parallel experiment with a large number of subexperiments to PDF, the operation may fail with timeout errors. The UI's "Print to PDF" function will fail to complete and the synchronous API endpoint "GET/entities/{eid}/pdf" will return a "502 Bad Gateway" or "504 Gateway Timeout" error.

Solution:
There are two recommended approaches to work around this limitation:
1. Use the asynchronous export API endpoints instead of the synchronous endpoint: Signals Notebook: How to use the asynchronous PDF export in the API
2. Export each section of the experiment individually and then merge in an external application

Note: The timeout limitation is a known constraint of the synchronous PDF generation process. The maximum number of subexperiments that can be successfully exported may vary depending on the complexity and size of the data in each subexperiment.