So I have this PLR ebook and what I want to do is give copies away as an incentive for joining my mailing list, but it has some affiliate links in there that I want to take out.. Can I do that? And is there some kind of software that I need to use to unlock the PDF file? Thanks!
In general, you probably are not allowed to take out those links if it was given away for free distribution. As with anything, it's your responsibility to read the full terms whenever you get your hands on PLR content (and if you're not given detailed terms, I'd be very suspicious of the outlet or person that gave it to you / sold it to you in the first place).
If the PLR product came with resale rights, or a Word source file than there's a good chance you're allowed to change the links. Go onto google and search for PDF editor.. I'm sure something will come up. Realistically, even if you're not allowed, who the hell is going to know?
Send an email asking the ebook creator about the issue. He put that affiliate links in there so he can make money out of it. If he say yes and the pdf is not protected go ahead and put your own affiliate links in there.
The fact that the file is protected in the first place should tell you something. So start by verifying that the e-book is actually PLR and not just one with resell / distribution rights. PLR can generally be edited, but they're also not generally protected, uneditable files. And ignore the advice suggesting no one's going to find out. E-book authors do in fact check on their work, even if not all. Violating copyright is breaking the law - never do anything just because you assume people won't find out. We very often do. Just check the rights with the original author. You may very well be allowed to edit it. Just don't do it without their consent.
I know of ebooks that are written and you can rebrand your original authors ebook with a pdf rebrander that only changes particular links. Check to see if there is a readme file with your package.