LibreOffice allows you to save document as a Template:
Go to File > Templates > Save
Click on My Templates and give it a name eg "Standard Report Template"
Then if you want you can set it as your default template:
Go to File > Templates > Organize, click into My Templates, and then on the saved Template, right clicl and select "Set As Default Template"
And all is good.
What if you have a bunch of documents and you need to change the template on already created docs?
Well first, you need to get the template changer from
When it downloads it doesn't have an extension, so you need to add ".oxt". Then goto Tools > Extension Manager
Click 'Add', select the .oxt file, and click Open.
Afterwards you'll notice two new options under Templates: Assign
This allows you to assign a template to an existing open doc, or to an entire folder.