Thumbnails are so obnoxious.  Spend all that time formatting everything just so, but when I attach a document, it inserts with the grace of an anvil.  

If it's an image (png, jpg, etc), sure, thumbnail it up.  Otherwise just do a link.  

The thumbnail also consumes resources to generate and store. The default should be the less-resource-intensive option, since many users accept the default without thinking.

Based on a question that I filed for this issue: https://community.atlassian.com/t5/Confluence-questions/Is-it-possible-to-Show-as-link-for-an-PDF-attachment-in-the-new/qaq-p/1096332?utm_source=atlcomm&utm_medium=email&utm_campaign=immediate_general_answer&utm_content=topic

An new issue was opened: 

https://jira.atlassian.com/browse/CONFCLOUD-65302

@Peter: I am using Confluence Cloud. I don't know how to get the version number, but the About Confluence screen shows: 1000.0.0c.... At the moment when you drag in a PDF you get a bland 'thumbnail' (no minimized preview of the PDF) with only the name of the PDF and the file size. I you edit, you have an additional delete button, and a checkmark if the tile becomes active. The function of it escapes me.

I checked, the behavior is the same for word and Excel documents.

Here an image in a save file:

Here an image of in edit view:

Also checked different browsers. My question 

@Marcel. What?? which version are you using? Confluence will be useless if we cannot link as url...

It looks that with the new editor (Cloud version) the possibility of 'Show as link' is removed from the functionality. So problem solved by removing the functionality (the new editor is a couple of steps backward).

Default to insert file as link - far better, more useful.

It's ridiculous. I had to upload 3000 files and now I have to go through them one by one to get a link view and remove the thumbnails. If I tried to do it all at once the whole instance collapsed so... Please do something about it.

Agreed, being able to specify this at the space level would be great as well

+1 vote. I, too, am constantly having to change attachments to links... and it gets tiresome really quickly. Confluence has nifty keyboard shortcuts to make working with it quick and easy, and I'd like to be able to drag and drop attachments equally quickly, without the need to change attachments to links one by one each time.