Strong box
Use an undamaged, preferably double-wall cardboard box and remove old labels.
Manduma.io
Pack it to arrive safely
A rigid box protects the contents and reduces courier correction charges.
No empty space
Wrap items and fill gaps until nothing moves when shaken.
H-tape method
Seal the centre and both edge seams with strong packing tape.
Label outside, details inside
Attach the PDF label flat and place a copy of both addresses inside.