In Writer for Mac, you have different options to change the rendering of Preview: its size, fonts or even background color.
Full-screen or Half-screen
Preview can appear as half of the screen side-by-side with the Editor or in full screen.
At full width, you can hide the Editor completely for an ideal reading environment, while half-width is often used by writers who want to keep track of the formatting as they go.
You can resize the Preview:
via the menu View → Preview Width → Split | Full
via the Toolbar (right side)
Web & PDF modes
You can choose between Web or PDF view.
You have more formatting options available for PDF via Settings → Templates.
In the Web view, you can invert the colors to mark the difference between the Editor and Preview.
If the Editor is in light mode, Preview will appear in dark mode and vice versa.
Fonts & Layout
Finally, you can modify the font and layout of the document in the Preview thanks to the Templates:
via the Toolbar (middle)
in the Menu select View → Templates
Preview determines what Export will look like. In the case of PDF, the currently selected typography in the Preview will be used.
A little extra…
If you are familiar with web development, you surely know the inspector tool lets you see parts of the code rendered by the page, such as HTML and CSS.
You can enable the Web Inspector tool in the Preview, in case you wanted to know what’s your document like, under the hood.
To enable Web Inspector in Preview, paste the following command into Terminal:
defaults write pro.writer.mac WebKitDeveloperExtras -bool true
In Writer for iOS, you have different options to change the rendering of Preview: the fonts, layout or even background color.
Web & PDF modes
You can choose between Web or PDF view.
You have more formatting options available for PDF via Settings → Templates.
In the Web view, you can invert the colors to mark the difference between the Editor and Preview.
If the Editor is in light mode, Preview will appear in dark mode and vice versa.
Fonts & Layout
You can modify the font and layout of the document in the Preview thanks to the Templates:
via the Toolbar (middle)
in the Menu select View → Templates
Preview determines what Export will look like. In the case of PDF, the currently selected typography in the Preview will be used.
In Writer for iPadOS, you have different options to change the rendering of Preview: its size, the fonts, or even background color.
Full-screen or Half-screen
Preview can appear as half of the screen side by side with the Editor or in full screen. At full width, you can hide the Editor completely for an ideal reading environment, while half width is often used by writers who want to keep track of the formatting as they go.
You can select between Split and Full Preview via the Toolbar with the “template” button.
Web & PDF modes
You can choose between Web mode or PDF mode. You have more formatting options available in PDF mode via Preferences → Templates.
In the Web mode, you can invert the colors to mark the difference between the Editor and Preview.
If the Editor is in light mode, Preview will appear in dark mode and vice versa.
Fonts & Layout
You can modify the font and layout of the document in the Preview thanks to the Templates via the Toolbar (via the template button)
Preview determines what Export will look like. In the case of PDF, the currently selected typography in the Preview will be used.
iA Writer for Android comes with a couple of in-app templates rendering in Preview.
Preview determines what Export will look like. You can change the rendering of Preview by switching Templates.
The ”template” button let you change the currently selected template.
Thanks to those templates, you can modify the font and layout of the rendered document.
In Writer for Windows, you have different options to change the rendering of Preview: the fonts, the layout or even background color.
Web & PDF modes
You can choose between Web mode (rendering HTML) or PDF mode: simply toggle ON and OFF the PDF mode on the top right of the Toolbar.
You have more formatting options available in PDF mode via Preferences → Templates.
If you make changes to your document, you can click the refresh button at the bottom right of the PDF preview to see these changes reflected.
In the Web mode, you can invert the colors to mark the difference between the Editor and Preview.
By default, Preview will scroll in parallel with the Editor. If you wish to scroll the panes independently, you can disable the parallel scrolling in File → Preferences → Editor → Synchronize Scroll.
Fonts & Layout
You can modify the font and layout of the document in the Preview thanks to the Templates:
via the Toolbar (middle of Preview)
in the Menu select View → Templates.
Preview determines what Export will look like. In the case of PDF, the currently selected typography in the Preview will be used.
A little extra…
If you are familiar with web development, you surely know the inspector tool lets you see parts of the code rendered by the page, such as HTML and CSS. You can enable the Web Inspector tool in the Preview, in case you wanted to know what your document is like, under the hood.
On Windows, you can enable the Chromium inspector by using CtrlJ.
Preview 
Preview can appear as half of the screen side by side with the Editor or in full screen. At full width, you can hide the Editor completely for an ideal reading environment, while half width is often used by writers who want to keep track of the formatting as they go.
You can select between Split and Full Preview via the Toolbar with the “template” button.
In the Web mode, you can invert the colors to mark the difference between the Editor and Preview.
If the Editor is in light mode, Preview will appear in dark mode and vice versa.
The ”template” button let you change the currently selected 
