Yes, you can. ClickHelp supports inserting videos from such video-sharing websites as Vimeo, YouTube, ScreenCast.com. To learn more, check out Insert Videos.

Yes, you can. Images are stored in your portal File Storage, and referenced in topics. You can replace a specific image file directly in the File Storage using the File Manager dialog in the main menu - all topics that use the screenshot will start showing the new image. We recommend that you store your screenshots and images in some logical folder structure rather than in a single folder - this makes the update process easier.

To create this kind of link, first, upload the file to be downloaded to the ClickHelp File Storage. Then, go to the the Insert tab of the Design View ribbon bar and click Link in the Links section. Choose the File link type and specify the URL to your downloadable file. Type the link text in the corresponding field and click OK.

Yes, you can create any link type. This functionality is available for you in the Insert tab of the topic editor’s ribbon bar - when you click Link, the Insert Link dialog gives you a choice of several link types.

Yes, this is possible with ClickHelp. As a rule, to use a paid font on some web resource, you just need to add the web resource domain name to the allowed domains in the font vendor licensing settings. For details, read this topic: Using Paid Fonts.

First, create a topic and fill it with your footer content. Make sure this topic is excluded from publishing (in the topic properties, set Do not publish) so it does not present in Table of Contents as an individual documents. Then, insert this footer topic into other topics as a Snippet - via the Single-Sourcing tab of the Design View. This will make it easier to update the footer in all topics at once.

To remove a footer/header snippet, switch to the editing mode for your topic, click the label of the Snippet (at the top-left of the Snippet box) and press Delete on your keyboard.

You need to add a style rule for the Paragraph element to your project CSS file. To learn how to open your project CSS file for editing, check this topic: Open a CSS Style File. Here is a sample CSS rule you can add in any place of the CSS file:

p
{
font-family: Calibri, Candara, Segoe, 'Segoe UI', Optima, Arial, sans-serif;
}

This rule above defines the font for all Paragraphs (that don't have inline styling, or specific CSS classes assigned). If some paragraph has inline styling that overrides this rule, you can use the Clear Format ribbon bar button to clear the inline formatting for that paragraph and use the default Paragraph style from the project CSS file.