Adding Watermark in Adobe JavaScript

Hello all,

my task is to add a Watermark based on key words in the pdf file on the first page. So if there is "DEST. 117.00 USD" in pdf file then add as a watermark "45125-123" if  there is in file "Credit note" then add watermark "457-125"  if nothing from above then add nothing. I checked it cannot be the situation when both variants "DEST. 117.00 USD" and "Credit note" can be in the file.

So, please help me to write a code in adobe JavaScript to solve this issue.

Please keep in mind that I am new to coding. I tried to write a part of the code.

Thanks for any support.

var pageArray = [];

var stringToSearchFor = "page\s1\sof\s1";

for (var p = 0; p < this.numPages; p++) {

// iterate over all words

for (var n = 0; n < this.getPageNumWords(p); n++) {

if (this.getPageNthWord(p, n) == "DEST. 117.00 USD") {
pageArray.push(p);
break;

}}

}
if (pageArray.length > 0) {

this.addWatermarkFromText({
cText: util.printd("45125-123", new Date()),
nHorizAlign: app.constants.align.center,
nVertAlign: app.constants.align.bottom,
nVertValue: 16, nFontSize: 10
});
}
else if (pageArray.length = 0) {

this.addWatermarkFromText({
cText: util.printd("457-125", new Date()),
nHorizAlign: app.constants.align.center,
nVertAlign: app.constants.align.bottom,
nVertValue: 15, nFontSize: 9

});}
else {}