Add Lines to PDF Document Online on Linux For Free

What do you like best?
I like the idea that I can edit a PDF document that is not machine fillable. I have been using this program for several years now in personal and not for profit business.
What do you dislike?
This is not the most user friendly program to use. It lacks a search field or help section to answer questions as how to do something I do not know how to do. It would be nice to be able to save a document as you are finishing instead of having to go back and rename a document. This is the case when I am using a master form that gets updated each month. I work on my laptop and the print screen has the print button to low. I see a sliver of the print button, that if I mess around with it for a while, I can eventually click on it. I can't be the only person with this problem. It would be helpful if the print screen could open a little higher on the screen, reduce some of the preface before the print button or have the print button on the top of the form. I also get frustrated with getting an actual signature in the system. There are no clear instructions on how to do that. It took me hours and hours to get my signature as part of the program. It would be nice to be able to scan a signature into the program. I have used Adobe DC with work in the past and I find it is a superior product, but not worth the cost with the volume of paperwork I need to do. Also a typical example of issues I have with PDFiller is the instruction to take a screen shot of my log in page. I have no idea of how to do that so I attached a PDF master document I use pdfiller to complete each month.
Recommendations to others considering the product:
Don't expect to see the most beautiful documents as far as how things line up, but it is certainly a way to complete PDF forms typed instead of hand written,
What problems are you solving with the product? What benefits have you realized?
As I stated above I use PDF filler with forms that are not fillable. I have used them to complete tax returns when a fillable form is not available. I have used them to sign a document instead of having to print, sign and rescan the document before sending it back to the originator. I have not used it to obtain other peoples signature

Great Tool! My experience has been great thus far. The use is seamless whether on my tablet, laptop, or phone, however, it's much easier to use on a laptop due to screen size. I am able to conduct business, receive faxes, scan items, edit forms, and more while on the go. This makes life a BREEZE! I am never really disconnected from work unless I choose to be. I would say the monthly payments are ongoing and never end. In real life, things like software have a finite value, however, I haven't seen an all-inclusive tool for less.