Hello, i need to render this project in to several sizes...1920x1080 DV PAL 1.09, 1280x720 DV PAL 1.09 and more...
I go to the composition settings window, change the size..click ok... but then my entire project..all the layers etc..alters. I need to resize all the layers, cjange the scale setting where there's a keyframe...all from the beginnig...how can I make AE adjust the comp automatically to the changes i made in the composition size?
The easiest way would be to render out a High Def master in a lossless format and then use Adobe Media Encoder to render out your other versions. You could also go directly to the AME with the After Effects project.
If you want to stay inside AE then nest your High Def comp inside compositions sized for your other output sizes and then Fit the nested master comp to the horizontal dimensions of the smaller comps. Make sure that the horizontal and vertical scale matches and you're good to go.
Composition --> Add Output Module. Add as many as needed and use the Stretch option to scale. Or render the master and create the versions in AME as Rick suggested. Whichever is easier...