How to change the paper size to A4 Size? I have replaced the A4 paper to my printer.

[DewiLee_01]

[A4Apollo]

Hey there! @DewiLee_01, Welcome to HP forums.

I understand you need to know how to change the paper size to A4 on your printer.

Don't worry I would like to help.

Please try the steps recommended below.

Load the custom-size paper into the paper input tray.
Open the item you want to print.
Click File, and then click Print.
In the Print window, click Preferences, Properties, or Printer Properties.
Click the Paper/Quality tab.
If Paper Size displays, select the new custom paper size in the Paper Size drop-down menu.
If Paper Size does not display, click Advanced, and then select A4 paper size from the list.
Click OK to close the Properties dialog box, and then click OK or Print to print the document.
 

Refer this article to know how to create custom paper sizes.

Let me know if this works!

Take Care! 🙂