文档广告的最佳实践是什么？请选择所有合适选项。

Optimizing documents for both desktop and mobile ensures accessibility and a good user experience across all devices, which is crucial for engagement. A compelling cover attracts attention and encourages users to open and read the document. Avoiding URLs within the document itself is a best practice because LinkedIn's document ads are designed to keep users within the platform; external links can disrupt the user flow and are not clickable within the document viewer. Keeping the file size under 100 MB guarantees faster loading times and a smoother experience for users, preventing frustration due to slow downloads or rendering issues. The option "仅使用不设访问门槛的文档" (only use documents without access gates) is incorrect because lead generation forms (access gates) are a common and effective feature of document ads to capture leads.