Here's a quick tip for you:
When you use SharePoint Online's modern 'Document Viewer' web-part, you'll notice that regardless of window size the height of the viewer is unusually 'short'.You won't even get a full view of a single page in most cases!
We can easily remedy this with only the tiniest bit of effort!
![soeyh_one](https://ohthreesixtyfive.files.wordpress.com/2018/04/soeyh_one2.png)
Then, click on 'Embed Information'.
![soeyh_two](https://ohthreesixtyfive.files.wordpress.com/2018/04/soeyh_two2.png)
![soeyh_three](https://ohthreesixtyfive.files.wordpress.com/2018/04/soeyh_three2.png)
Its sacrifice will not be in vain, however, since we will be taking the handy little embed code it gave us to use in a new Embed web part.
![soeyh_four](https://ohthreesixtyfive.files.wordpress.com/2018/04/soeyh_four2.png)
Paste the embed code into the Embed web part settings pane.
![soeyh_five](https://ohthreesixtyfive.files.wordpress.com/2018/04/soeyh_five2.png)
As you can see highlighted above, we're going to change the embed code's default height value (which for me was a measly 677 pixels).
I chose a more suitable value of '1120px', but you are welcome to toy around with it until it displays your document just right.
In the end, you'll be welcomed with a much more useful display of your document!
![soeyh_six](https://ohthreesixtyfive.files.wordpress.com/2018/04/soeyh_six.png)