Of course it is possible to convert the PDF to word and then add notes to it. After that you may convert the word file back to PDF again. However this way is a little time-consuming and you can make sure that the pattern of PDF will be changed or not. Now it has be more flexible to write notes on PDF with the programs. I would like to share the two free online ways. Way 1 Use LightPDF Steps 1. Visit Edit PDF s function page on LightPDF. 2. Drag your file from yourputer hard disk and drop it on its interface. 3. After loading your PDF file select one of the tools including pen circle highlighter pen to add notes to the PDF file. 4. After adding the notes click the Save icon to save the file. 5. When it finishes processing it download the file to yourputer. Features of it This service is totally free to use but its functions for adding notes to PDF are not very powerful. You are not required to download any program for using the editing feature on LightPDF website. There is no any restriction for using all other functions of this online service. All inputted and outputted files will be deleted automatically from its server. Way 2 Use PDFescape Steps 1. Visit PDFescape s website. Upload your file onto this website. 2. Take notes on your PDF file using the tools like whiteout freehand form field and so on. 3. Click Download & Save button to save your edited file. Features of it Free users can only upload PDF which is less than 1 MB and 1 pages. Support loading PDF file by just pasting URL. Support adding annotations in various styles including sticky note skrikeout underline rectangle etc.