If you put an image inside the text flow and PDF export that page, the image is placed on an own line, see attachments.

My suggestion is its related to the fix from CONF-36376 and the current situation is surely better, but still not good.

Expected Result

Actual Results

Workaround

1. Choose the cog icon, then choose General Configuration under Confluence Administration
2. Choose Look and Feel > PDF Stylesheet. The following screen allows you to enter and save CSS code that will render content on each page and enter the following
3. Insert the code below into the field and clink on save.

    img.confluence-embedded-image {  
           display: inline-block !important;  
   }