Splitting a PDF page in two

You can use mutool, a MuPDF command-line tool (sudo apt-get install mupdf-tools):

mutool poster -x 2 input.pdf output.pdf

You can also use -y if you want to perform a vertical split.

Try Gscan2pdf, which you can download from the Software Centre or which you can install from command line sudo apt-get install gscan2pdf.

Open Gscan2Pdf:

1. file > import your PDF file;

   

   Now you have a single page (see the left column):

   

2. then tools > Clean up;

   

3. select double as layout and #output pages as 2, then click OK;

   

4. Gscan2pdf splits your document (among other things, it will also clean it up and deskew it etc.) Now you have two pages:

   

5. Save your PDF file if you're satisfied with the result.

I would use Briss. It lets you select various regions of each page, each of which to turn into a new page.