How can I reduce the time-taken by Microsoft Word while saving a large document?

Make sure that all of your formatting is done using Styles with no manual page breaks.

Here is my writing on this.

For long documents, documents that are likely to be heavily edited, and documents that may form the basis for other documents, follow the basic rule that to change formatting use Styles... Do not apply direct formatting.

In Ribbon versions of Word (2007+) this is even easier, click on your style from the Styles gallery!

You will save yourself, and others, untold hours of hair-tearing. For shorter one-use documents, direct formatting is OK; you'll only regret not using styles about one time in six, on the other five out of the six, you'll save a bit of time. If you create document templates with direct formatting, you deserve what will happen to you when someone finds out (and it won't be nice). In my opinion, using direct formatting in document templates intended for use by others rates the words malicious and/or incompetent. If the templates are for your own use, you deserve the loss of days, months, even years from your life that you'll spend fighting with Word and trying to figure out why your documents look so bad.

Trying to use Word without understanding and using styles is like pushing on a string. I resisted learning and using styles for years and now regret every day of those years because although that string was still very hard to push, it kept getting longer and longer, and had some very important projects tied to it! Once you understand styles and the Word concept of organizing things into Chinese boxes everything falls into place and instead of pushing a string, you can push a button that turns on the very powerful text processing machine known as Microsoft Word and it will start doing your work for you instead of running around behind you trying to undo what you thought you just did.

These statements should be even stronger for those using Word 2007-19 because styles are even easier to use in the ribbon versions of Word.

I just had occasion to edit a 100-page document that was created without using styles. It was formatted completely with direct formatting. Each page ended with a page break.

Each time it had to be saved, the save took more than 60 seconds, during which time Word was frozen.

A similar-sized document formatted using Styles takes less than 3 seconds for me to save. When a page break must be forced, instead of using a manual page break, the paragraph to begin the new page is formatted using a style that has "page break before" paragraph formatting.

This difference was due entirely to the document being directly formatted - a much higher level of complexity. Each paragraph mark in a directly-formatted paragraph carries with it up to fifty different formatting commands. When formatted using a style, that paragraph mark will carry with it one command - use this style!

--CKK 1 Feb 2012

See an example of a document formatted using styles for two virtually identical documents, one formatted using Styles, the other mostly not using Styles. Both have the same number of words and pages. One is 34K; the other is 48K.

--CKK 6 Jan 2016

In this Word Forum thread, the poster was having a very sluggish response from Word. I advised changing formatting from direct formatting to style-based. Problem solved!

--CKK 30 Oct 2019

See also: Yet Another "Use Styles" Verbal Beating! by Dian Chapman, MVP