How can I combine PDFs in LibreOffice?

I'd like to be able to simply drag a pdf file into the pages explorer of a pdf that's being edited. This has no effect and dragging the file into the work area on a new page results in something like the follow:

I've also tried 'file>insert' and selecting the pdf which results in an error saying 'the file could not be loaded'.

How can I go about inserting a pdf as a page or set of pages in a pdf document I'm working on?

To combine pages from two PDFs in LibreOffice Writer follow these steps.

1. Open the first PDF document in LibreOffice Writer using File -> Open.

2. Open the second PDF document in a new LibreOffice Writer window using File -> Open.

3. Select a page in the first PDF document Pages pane before where you want to add a new page in the PDF document.

4. Select the page you want to add from the second LibreOffice window and copy it.

5. Paste the new page into the first LibreOffice Writer window.

6. Export the new PDF file using File -> Export as PDF... -> click the Export button -> click the Save button -> browse to the location where the newly created PDF file will be saved.

LibreOffice Draw

It seems that you can combine them in Draw.

http://www.techrepublic.com/blog/tr-dojo/edit-pdf-documents-with-libreoffice-draw/

pdfsam

However my real suggestion would be to use

http://www.pdfsam.org/

GhostScript/PDFTK

Edit: On Linux you can use GhostScript and pdftk

https://stackoverflow.com/a/8159842/2982543

http://www.ghostscript.com/download/gsdnld.html

https://www.pdflabs.com/tools/pdftk-server/#download