1) I can't respond at length at the moment, but for some reason, the attachment to your last post didn't work and all we get is an invalid link. Please try posting it again.
2) What type of file were you trying to post? Unless it is a JPG or GIF, you'll need to zip it before the forum software will accept it.
3) Please respond to my previous question:
"...Are your cartoons contone (ie, continuous tone) artwork such as one might get from the original artists, or half-tone (ie, scans of pages mass produced by a large volume offset press, ie that are made up of a lot of tiny dots)?..."
4) Exactly what model laser printer are you using? When you go to print a document, do you ever see a dialog box put up by your printer driver asking what size you want the print, or do you only see the print dialog box put up by Photoshop?
5) Finally, you state:
"... I printed a master sample and in my opinion it looks good but I still need your advices before committing any big mistake. I digitally stretched the picture in a way that the final print has a white border all around (decided by the printer) but nothing is cut out from the picture. ..."
In order to give you good advice, I need to know many more details about exactly how you got the image, and what you may have done to it before and after you "digitally stretched" it.
For example, did you scan some half-tone reproduction of the cartoon, or do you have the original artwork. If you scanned some object, exactly what settings did you use? What were the linear dimensions (in inches or cm) of the object you scanned? What dpi did you use in scanning? Did you do anything else to it before you "digitally stretched" it? For example, did you change the dpi or pixel dimensions (with or without resampling) before you "digitally stretched" it? When you "digitally stretched it", I presume you went into transform mode in Photoshop and dragged one corner of the image. Is that correct, or did you do something else to "digitally stretch it"?
TomM