There are several ways to share documents between site collections, and we are going to show some of them here. Common for all is that you should have the shared documents in one place, so that you don't have to change in several places when the documents are edited. That is why copy and paste documents is a bad idea.
In the two first demos below Peter Kalmstrom, CEO and Systems Designer of kalmstrom.com Business Solutions, shows two ways of sharing documents between site collections: to embed Word files and to gather all files with a certain tag in a Content Search web part.
SharePoint only shows files to those who have permissions to see them, so when you decide sharing option you must consider how the page will look for people who have access to the page but not to the shared files. In the third demo Peter shows how the two option behaves to a user without access to these specific files.
Peter starts with adding an Enterprise Keywords column to a SharePoit library that contains files he wants to share. This makes them easy to find in filtering and searching. This is shown in the first demo below.
Add an Enterprise Keywords column to a list
Click on the Library Settings button under the LIBRARY tab in the ribbon.
Click on the link Enterprise Metadata and Keyword Settings in the Permissions and Management group.
Check the box to add an Enterprise Keywords column. Click OK
Add keywords to the documents you want to share with other site collections. (This is quickly done in the Quick Edit mode.)
Peter continues the first demo by embedding a file. Note that this is only possible for Word, PDF and PowerPoint files. (The second method, Content Search, works with all file types.)
Embed a file
Select the file you want to embed and click on the ellipsis (...).
Click on the Menu icon and select Embed Information.
Copy the code and click OK.
Open the page where you want to place the embeded file in Edit mode.
Click on the Embed Code button under the INSERT tab in the ribbon and paste the code you copied. (You may also edit the code.) Click on Insert and Save the page.
Share files in the Content Seach web part
This method is a quick way to gather files from several site collections on one page. It gives links to all files that are tagged with a certain keyword.
Open the page where you want to place the embedded file in Edit mode.
Click on the Web Part button under the INSERT tab in the ribbon.
Select the 'Content Search' web part in the 'Content Rollup' category. Click on Add.
Edit the web part to only show documents that are tagged in a certain way.
Click on the 'Change query' button.
Select the query 'Items matching a tag (System)'.
Select to not restrict the results by app if you want to have files from the whole tenancy.
Restrict the results by tag and enter the tag you wish to use.
Define the other settings for the web part and click on Apply and Save the page.
SharePoint only shows what you have permission to see, so what happens when a user without access to the shared files opens a page where they are gathered?
This is an important consideration, and generally the Content Search option is to prefer in that respect. In the demo below Peter shows how the two options look to a user who has no right to see the files.