Easy way to configure the page size in Google Docs to any of the A sizes:
4A0, 2A0, A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10 and also important envelope sizes: DIN lang (DL), C4 C5, C6, C6/5

Google Docs does not support custom page sizes, with this addon you can set any of the A* page sizes in portrait or landscape orientation.

Size		Width x Height (mm)	Width x Height (in)
4A0		1682 x 2378 mm		66.2 x 93.6 in
2A0		1189 x 1682 mm		46.8 x 66.2 in
A0		841 x 1189 mm		33.1 x 46.8 in
A1		594 x 841 mm		23.4 x 33.1 in
A2		420 x 594 mm		16.5 x 23.4 in
A3		297 x 420 mm		11.7 x 16.5 in
A4		210 x 297 mm		8.3 x 11.7 in
A5		148 x 210 mm		5.8 x 8.3 in
A6		105 x 148 mm		4.1 x 5.8 in
A7		74 x 105 mm			2.9 x 4.1 in
A8		52 x 74 mm			2.0 x 2.9 in
A9		37 x 52 mm			1.5 x 2.0 in
A10		26 x 37 mm			1.0 x 1.5 in
DL		220 x 110 mm
C4           229 x 324 mm
C5          162 x 229 mm
C6          114 x 162 mm
C6/5      114 x 229 mm

This addon only sets the page size and page orientation. Use File → Page setup to set all other page settings. As that dialog does not support custom page sizes it will reset your page size. Simply use the add-on menu again to set your custom page size.

Note. This add-on is meant as a short cut to quickly set any of the DIN A page sizes (A1, A2 ...). If you want to set an arbitrary page size please use https://chrome.google.com/webstore/detail/page-sizer/acgkneeneageffjinlglednnehpelffb