What is the logic behind X and Y axis in PDF?

Question

I'm updating a PDF dynamically using TCPDF and FPDI. Everything works properly there.

However, I cannot understand the way SetXY() works.

What are exactly the X and Y axis values? Milimeters? Letter spacing from the edge?

Thanks!

Answer 1

They're measured in millimeters by default. However you can change it using the function setPageUnit.

The X (abscissa) and Y (ordinate) values are by default started from the top-left hand side of the document/page. However this can be changed using RTL (right-to-left) mode using the setRTL function.