How do I delete certain pages

Deleting pages will only work in Adobe Acrobat, not the free Reader. If that is not a problem, you can use the "word finder" to find a certain word on a page. You would do this by iterating over all pages in your document, and then over all words on that page. You would use code like this:

for (var p=this.numPages-1; p>=0; p--) {
    for (var n=0; n<this.getPageNumWords(p); n++) {
        if (this.getPageNthWord(p, n) == "TheWord") {
            this.deletePages(p);
            break;
        }
    }
}

This will loop over all pages, starting at the end of the document (so that when you remove a certain page, the page numbers before that page will not change).

Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com

I would like to be able to delete several pages at the same time using this method i.e to delete page X contains the word 3A and the page X+1 contains the word 3B.

You need to add more cases to the part of the script that checks if the word exists:

if (this.getPageNthWord(p, n) == "3A") {
        this.deletePages(p);
        break;
}
else if (this.getPageNthWord(p, n) == "3B") {
        this.deletePages(p);
        break;
}

Because there is some overhead in actually getting the word, you may want to get it only once and then use a variable in your actual comparison:

var theCurrentWord = this.getPageNthWord(p, n);
if (theCurrentWord == "3A") {
    this.deletePages(p);
    break;
}
else if (theCurrentWord == "3B") {
    this.deletePages(p);
    break;
}

Also instead of to look through all the document and find the specific word(s), is it possible to point a section on it and then to look for the word(s)?

Not with JavaScript. You can select a word, but you cannot get the word that is currently selected.

Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com

From a different question posted by Alain:

Is it possible to move to a page using "Go to a page view" and delete the 4 following pages after the current page?

How would you move to a different page? Would the user select the page, or would this be done by e.g. clicking on a bookmark or a link?

In general, you can find out what the current page is, and based on that, you can select the next four pages.

Let's assume you have a menu item that the user triggers when the pages should be deleted, you can then use the following script to delete the next four pages.

// delete the four pages following the current page

for (var p=this.pageNum+4; p>this.pageNum; p--) {
    if (p < this.numPages) 
        this.deletePages(p);
}

Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com