PDF Bob is described as 'Online PDF editor. Edit PDF, annotate PDF, manage PDF pages, edit PDF text, highlight text in PDF and much more. Export files to PDF, Word, JPG and PNG formats' and is an website in the Office & Productivity category. There are more than 10 alternatives to PDF Bob, not only websites but also apps for a variety of platforms, including Windows, Mac, Linux and iPhone. The best alternative is Adobe Acrobat DC. It's not free, so if you're looking for a free alternative, you could try Master PDF Editor or Sejda. Other great sites and apps similar to PDF Bob are PDF Expert (Paid), PDF-Shuffler (Free, Open Source), DeftPDF (Free) and PDF24 Tools (Free).
PDF Expert lets you read and annotate PDF documents, highlight text, make notes and save these changes being compatible with Preview and Adobe Acrobat. Moreover, PDF Expert is the only iPhone application that can fill PDF forms!
LightPDF is the best free online PDF tool that allows you to edit and convert PDF. Also, you can use it to convert other types of files to PDF. It is quite easy and safe to use. No watermark, no plugins and no limits to the time or size.