Simple PDF Upload & Link

Hi FTW. There are many ways to access files in Backdrop, depending on what you want to do. BTW, they are very similar to how Drupal 7 worked (so, there is nothing especially obscure in Backdrop).

Without using the Backdrop UI:

•  FTP the file into your public files folder of your site (typically, the folder files in your root installation). Or if you use cPanel in your shared hosting, you can use the File Manager there to upload it.
•  Add a link to it in your node body (or in a custom block) using the URL, for example either https://example.com/files/MYFILE.pdf or /files/MYFILE.pdf 

If you want to use the UI you can either attach a field to a content type and allow for pdf file uploads, or you can use the Content > Manage files to upload it. This may help too: https://docs.backdropcms.org/documentation/working-with-files

There are other ways too. For example you can upload a file (or select an existing uploaded managed file) using CKEditor in a body field.

I'll try to help.

In the admin menu, go to edit the content type in which you want to add a PDF file field - for the example I'm using the standard Page content type.

admin/structure/types/manage/page

Switch the top tab to MANAGE FIELDS

In the Add a new field line, select a File type field and save the page with the Save button. You should also give the field a name, for example let it be a PDF file.

In the new page, do not make any changes and press the SAVE FIELD SETTINGS button

On the next page, type in Allowed file extensions - pdf and a folder in which to save the files on the web server - for example – pdf-files.

Below in the field Global settings, enter how many files will be able to be uploaded or choose an unlimited number.

Save this form as well.

After these settings, when creating content of the Page type, you will now be able to attach a PDF file.

@amilenkov's answer is good if you want a custom field to make attaching and displaying PDFs easy.

One more way that you can do it is through the editor itself, if you'd rather upload and attach/link files directly in the CKEditor interface.

Under Configuration > Content authoring > Text editors and formats, choose the format that you want to allow file uploads in (it should have CKEditor enabled) and click "Configure":

Scroll down and look for "File uploading" (check the box to enable and configure):

Now when you use this text format and click the link icon in the editor, you'll see an option to "Upload a file and link to it":

Thanks for this advice. I had an idea that it could be done in a similar way, but I didn't know exactly how to do it or I have simply overlooked a useful opportunity.

I have been studying Drupal / Backdrop since 2010, but I am very far from knowing all the possibilities of the system despite the fact that I consider myself an experienced user after developing a large number of websites with Drupal 5, 6 and 7.

But this specific question makes me think:

The community is very focused on helping Drupal 7 users migrate to Backdrop. What seems to be somewhat overlooked in this process is that Backdrop, like Drupal, has a very steep learning curve for users who have never learned Drupal (and they will become more and more so given the direction Drupal is going ) and should probably be supported more effectively. With the premise that work techniques common to Drupal users are completely unknown to them.

I also have a specific idea. This forum is extremely helpful, but not in the capacity of a textbook or guide. The responses in the forum are scattered in various topics and lack didactic organization. If the Backdrop CMS User Guide were somehow augmented with frequently asked questions from the forum related to the User Guide topics, that would be useful to a large pool of potential Backdrop users. And that potential would become bigger and bigger as the number of people who have experience with Drupal 7 decreases .

In my previous comment, I was focused on the goal of offering a proposal as simple as possible for uploading PDF files, and I know for myself that there are still quite a few complex details to this specific know-to that are overlooked in the explanation of this technique. For example the questions about how this file field is displayed and the options for settings there - I assumed the default settings would work well enough.

Now I want to add that, in addition to the method through the CKE editor, suggested by laryn (which method is also easy and very suitable), I have also come across a significant number of additional modules dedicated to working with PDF files.

https://backdropcms.org/modules?s=pdf

In general, new users should realize that Backdrop is a system with really huge capabilities, surpassing almost everything else, but learning all these capabilities takes time and persistence.

It seems to me that emphasizing that learning Backdrop is easy work is a false marketing perspective. No, learning is quite difficult for newcomers, it requires a lot of time and effort, but it pays off with the incredible capabilities of the system (compared for example to the ubiquitous WordPress), and this is what new users should know from the beginning so that they do not quickly lose confidence in the Backdrop or, even worse, in their own cognitive potential.