nicmare

Did you know that WordPress generates a thumbnail image file when uploading a PDF-file? This works when the PHP Extension imagick and Ghostscript is available! It won’t work with GD library! You know they are present and it’s working, when you upload a PDF-file in the media library and you immediately see a thumbnail of the file. Now that thumbnails are available my plugin hooks into the Gutenberg file-block to automagically inserting that thumbnail right before the file block. Besides that it also provides some more options:
<h3>Plugin Features</h3>
<ul>
<li>a toggle to insert an preview image before the file block</li>
<li>a toggle to link the preview image with the “link to” settings value of the file block</li>
<li>a toggle to link the preview image with itself to the full-size image</li>
<li>a toggle to enable the Lightbox-Effect on the preview image (enable in settings)</li>
<li>a setting to choose the size of the preview image: thumbnail, medium, large</li>
<li>a settings page to define default for image size and <code>show inline embed</code> default value and a <code>height in pixels</code> default value</li>
<li>when activating the plugin, the <code>show inline embed</code> option of the file block gets disabled by default</li>
<li>the preview image link target is based on setting of file-block (<code>open in new tab</code>)</li>
<li>adds new block styles to file block with just a few inline css code</li>
<li>this plugins main goal is to be very lightweight and avoid loading any additional assets and saving DOM performance. It just uses 3 files. </li>
</ul>
This plugin requires imagick and Ghostscript! A good WordPress web hosting has it installed by default.

PDF-Preview inside File-Block

Extends the core/file block to optionally insert a PDF preview image (generated by WordPress) before the file block and adds linking/lightbox options.

eugenealegiojo

The plugin that will let admin user to add download links to any posts/pages in simplest way and hassle free. 
Allows all your site visitors to download any files from your website without any user restriction.
<h4>Features</h4>
<ul>
<li>Downloader button is available in your admin content editor for post, page or post type. Shortcode will be generated automatically.</li>
<li>Insert download links manually via shortcode [media-downloader] to any posts, pages or custom post types. Check for more parameters below (Embedding).</li>
<li>Allow users to directly download in all file formats for free.</li>
<li>No file size limit for downloads. 
For more information please check the <a href="http://phplugins.softanalyzer.com/simple-file-downloader/" rel="nofollow ugc">Simple File Downloader</a> documentation page</li>
</ul>
<h4>Embedding / generated Shortcodes</h4>
Create a new post/page and click the ‘Add Download’ button from the content editor, then generate the shortcode below:
<pre><code>[media-downloader media_id="9" texts="Download Now!"]
</code></pre>
Media id is automatically added from your media library.
Here are the all the available parameters when generating shortcode for file download:
texts
If you choose to leave the texts parameter empty, then it be defaulted to ‘Download File’.
image_url
You can also use image/button as your download link. If you supplied this parameter, then texts parameter will be replaced by this image.
<pre><code>[media-downloader media_id="9" image_url="http://domain.com/wp-content/themes/images/button.png"]
</code></pre>
class
You can add class to your download link either a texts or image button. This is useful if you want to apply your own style.
<pre><code>[media-downloader media_id="9" texts="Download PDF" class="download-pdf"]
</code></pre>
display_filesize
You also have an option to display the size of the file. Just set it to ‘yes’
<pre><code>[media-downloader media_id="9" texts="Download PDF" display_filesize="yes"]
</code></pre>

Simple File Downloader

Simplest way to add download links into your posts/pages.

PDF-Preview inside File-Block vs Simple File Downloader