Publisher allows you to open previously saved documents.
A key feature of the Affinity product range is the ability to seamlessly open any Affinity project file in any Affinity product, regardless of the original Affinity product it was created in. In doing so, you can enhance your design with another Affinity product's features with no concern over file compatibility on saving.
To open a document:
Do one of the following:
From the File menu, click Open.
Double-click anywhere in the empty view. (Only available when no other documents are open.)
Select the file you want and click Open.
To open a recently used document:
From the File menu, click Open Recent, then select a file from the submenu.
To open a document template:
From the File menu, click Open.
Select the .aftemplate file you want and click Open.
Opening Affinity Designer documents
On opening an artboard-based Affinity Designer document in Publisher, you will be presented with its artboards. To convert them to spreads, select Convert Artboards to Spreads on the Pages panel. The resulting spreads will work like any other spread and match the original artboards' dimensions.
After converting a document, save it as a new Affinity Publisher document and retain your original file in artboard format for editing.