Find an online PDF creator which is designed to convert various documents to PDF.
online2pdf is my favorite online free service to save images as PDF. It is a free platform allowing users to convert Word, Excel, PowerPoint, IMAGE, Text and so on to PDF, even you can merge, compress and protect PDF outputs when saving these files as PDF. Furthermore, users can export PDF to Word, Excel, PowerPoint and images.
I use Free Movavi PDF Online Editor https://pdfmovavi.com/convert-png-to-pdf It is very simply to use, you will get high quality and never regret about it. Movavi is a must have on any desktop. Good luck!