pdfxup: add page (#8196)

* pdfxup: add page

* pdfxup: change description to start with uppercase letter

* Update pages/linux/pdfxup.md

Co-authored-by: CleanMachine1 <78213164+CleanMachine1@users.noreply.github.com>

* Update pages/linux/pdfxup.md

Co-authored-by: CleanMachine1 <78213164+CleanMachine1@users.noreply.github.com>

* Update pages/linux/pdfxup.md

Co-authored-by: CleanMachine1 <78213164+CleanMachine1@users.noreply.github.com>

* Update pages/linux/pdfxup.md

Co-authored-by: marchersimon <50295997+marchersimon@users.noreply.github.com>

* pdfxup: add explaination of the meaning of N-up

* Update pages/linux/pdfxup.md

Co-authored-by: marchersimon <50295997+marchersimon@users.noreply.github.com>

Co-authored-by: CleanMachine1 <78213164+CleanMachine1@users.noreply.github.com>
Co-authored-by: marchersimon <50295997+marchersimon@users.noreply.github.com>

pages/linux/pdfxup.md

@@ -0,0 +1,17 @@
+# pdfxup
+
+> N-up PDF pages.
+> N-upping means putting multiple pages onto one page by scaling and rotating them into a grid.
+> More information: <https://ctan.org/pkg/pdfxup>.
+
+- Create a 2-up PDF:
+
+`pdfxup -o {{path/to/output.pdf}} {{path/to/input.pdf}}`
+
+- Create a PDF with 3 columns and 2 lines per page:
+
+`pdfxup -x {{3}} -y {{2}} -o {{path/to/output.pdf}} {{path/to/input.pdf}}`
+
+- Create a PDF in booklet mode (2-up, and pages are sorted to form a book when folded):
+
+`pdfxup -b -o {{path/to/output.pdf}} {{path/to/input.pdf}}`