docs: Update docs with preferred way of displaying documents #2291

[marek-mihok]

The PR fulfills these requirements: (check all the apply)

• It's submitted to the main branch.
• When resolving a specific issue, it's referenced in the PR's title (e.g. feat: Add a button #xxx, where "xxx" is the issue number).
• When resolving a specific issue, the PR description includes Closes #xxx, where "xxx" is the issue number.
• If changes were made to ui folder, unit tests (make test) still pass.
• New/updated tests are included

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Closes #2291

[marek-mihok]

For some reason PDF in /docs/widgets/form/frame/#with-document section is not rendered:

The path seems to be correct. @mturoci could you please check where could be the problem?

[mturoci]

@marek-mihok the problem is in Playwright - headless mode does not render pdfs for some reason, but headed does. See #2314.