You want to get your book published but you don’t want to give a copy to a publisher to determine if t think it is worth publishing? WTF? If it gives you any solace, when you make the PDF, you can password protect it. Give the PDF and password to the publisher. If another publisher requests a copy, give them a PDF with a different password. Then if your ms gets heisted, you trace who leaked it and sue them. Of course, you are taking the chance of insulting the very people you are trying to establish a business relationship with … by indicating you don’t think t are trustworthy. Send the damned PDF, sheesh! (PS, I get pre-publication book PDFs to review all of the time. In the old days this was an actual book with a special cover on it (For Review Purposes Only!). You can find such copies occasionally in used book stores. It is very hard work to steal such a book and you would be easily caught if you do. There are easier ways to steal money.)
And last but certainly not least, a professional would not be caught red-handed or caught on hidden camera if his partner was the one who stole it. If your ms is not a writer, she should not review this book for your book club.