When creating a Job Listing or Listing Template, you will have a formatted text editor where you can create formatted text (e.g. bold, bullets, font size, etc), just like a word processing program. If you already have your text in an existing document, such as a Microsoft Word document or web page, you can copy/paste from the document into the editor using the standard copy / paste clipboard commands.
If you do copy from an existing document source, it is recommended that you paste into the ApplicantStack editor using the Paste as Text command button.
The Paste as Text command will paste in the text and line breaks, but will NOT bring over any of the formatting from the source. You will then need to apply the desired formatting using the toolbar (bold text, bullet lists, etc). Although this is an extra step, this is the recommended method because it ensures your job description will look clean and consistent on your website.
The problem with copying over formatting from a source document is that the formatting is often different from the formatting of your website, where the job description will appear. For example, you may have Arial font in your document but your website uses Verdana. Or your website text might have a slightly different color or size. And once you bring the formatting over it can be hard or impossible to fix using the toolbar, which can only override some styling. This is especially true of Microsoft Word documents which copy formatting with the intent of recreating the exact printed document, which is not what you want on a web page.
Note that if your source is a relatively "clean" Microsoft Word document, you can try using the Paste from Word command button. This does a reasonable job of trying to remove the physical formatting from a Word document while retaining the key formats like bold and bullet lists.