White lines after exporting to PDF from Illustrator

[Edo7152]

Hi everyone, I apologize initially for possible grammatical errors.
As written in the title, when I go to export to pdf from illustrator, white lines appear that follow the segments of the illustration.

In illustrator, however, the file is perfect.

I tried to read and do all the tests that I found in this forum, in others and followed a thousand other tips (such as disabling or changing the anti-aliasing settings). The only real solution I have found is to open the polygons in order to place them under others (placed in the foreground). Now, I'm still a beginner with Ilustrator and I probably did something that I shouldn't have.

In my opinion, the problem was created because, once I made a polygon over the initial shape, I then went to use the white arrow (A) to drag an anchor point over an already existing one ... in fact going to expand the segments in so that they are no longer "precise" the white lines disappear.

 Can you recommend a method to solve everything as quickly as possible? Because I tried to enlarge the polygons by hand and it works but I have to fix 10 illustrations all composed of a myriad of polygons.

Edit: I'm using Windows 10 pro and Illustrator is the latest version avaible 

Edit 2: 

I tried to export the file in .tiff and instead of the lines it seems that a blurred halo appeared ...
 they are always better than before but it is not perfect and it is not a pdf

Last Edit:

I tried to duplicate the layer, copy it to one below and convert it to grayscale and now I tried to export it to pdf and it seems ok

... at least .. it is for me haha

[Lukas Engqvist]

Do you havepixel grid or snapping functions active? What scale is it you are drawing at? Are these primitives filled with single colours or are they masked shapes? How are you viewing the PDF (What PDF viewer Acrobat Pro DC or some other reader)? Are the colours spot colours? Lines that you get between shapes like that, when they do not scale with the artwork in the viewing application can be caused by anti-aliasing. The technology may be smoothing the jaggies of the screen to give you a smoother experience than the number of pixels allow, but has the side effect of rounding upp/down which may at times result in a hairline between solid colour patches. Did you create the fields as areas with fill colour or did you also have a stroke when drawing the artwork?  In Adobe Acrobat you can turn off "smooth graphics", and if you have a retina display they jaggies are so small this will both improve the display and make the preview faster. In lowere resolution screens you can use this to see if the lines will appear on print or if they are just dispay artifacts. It seems you found a workaround? 

[Edo7152]

As said before, I am still a little inexperienced with AI however I can say that I am working in CMYK at 300 ppi ... The scale to which I made the screenshots was the maximum value (at 100% the lines could be seen but not very well ).
As for anti-aliasing I can be sure that it is not because I have tried 6 different devices, such as Ipad pro, iphone xs and other PCs with correctly calibrated monitors (all in 4k).
To open the pdf I use Acrobat but also changing the options on the display page does not change anything ... A friend of mine sent me her work in pdf to test it and I opened it with chrome..it was all perfect.
For now I can say that I have solved it, next time I will try not to make the same mistakes. Thanks a lot.