Accepted answer

I figured it out! Had to do some fiddling with css to make it work but it looks fine now. In my theme, there was link styling like this:

a {
  padding: 5px 0;
  display: inline-block;
}

So I added this exception for text within paragraphs (<p> tags):

p > a {
  display: unset;
}

Doesn't appear to have broken anything else. 

Most helpful answers

I would give this module a try.  https://backdropcms.org/project/pdf_to_image

I use it and it's Drupal counterpart.  https://www.drupal.org/project/pdfpreview

The modules can be setup to display a file upload field as an image.  Uploading the pdf generates an image of the first page and that links to the rest of the pdf.

I use this in paragraphs and it is a solution for a field, not really adding pdfs to a body field.

Comments

OK, reading the documentation on that at https://github.com/backdrop-contrib/image_url_formatter it looks like it works with image fields not with inline images. Am I missing something?

Trying out in the CKEditor (4) window, I can link an inserted image to a doc but it messes up the image formatting. i.e. it no longer floats at left / right as set. Any easy solution for this?

Thanks.

I figured it out! Had to do some fiddling with css to make it work but it looks fine now. In my theme, there was link styling like this:

a {
  padding: 5px 0;
  display: inline-block;
}

So I added this exception for text within paragraphs (<p> tags):

p > a {
  display: unset;
}

Doesn't appear to have broken anything else. 

I would give this module a try.  https://backdropcms.org/project/pdf_to_image

I use it and it's Drupal counterpart.  https://www.drupal.org/project/pdfpreview

The modules can be setup to display a file upload field as an image.  Uploading the pdf generates an image of the first page and that links to the rest of the pdf.

I use this in paragraphs and it is a solution for a field, not really adding pdfs to a body field.

@keiserjb - Thanks for your suggestion. You say:

it is a solution for a field, not really adding pdfs to a body field.

So this also is for a file field, though taking a little different approach, and not for inline images?

I do like this module's functions, though. How do you use it with Paragraphs?

The way you suggest is better because it automatically generates the preview image and links to the doc. I'll put it on my list to try it in the future.

Separately, I had built a site for a friend some years ago using D8 but she found it too difficult to use and so it never gets updated. I was thinking of converting it over to Backdrop, hence my post in this forum about converting from D9, but I'm pretty sure she would not like this kind of extra complexity of using a file field.