Converting an existing PDF document to a new PDF/A document
To archive your electronic documents with long-term preservation you will need to convert your source PDF document to a PDF/A document intended for archiving.
Our native PDF to PDF/A converter parses the source document and compares the document structure to the expected conformance level. The document can be modified to conform to the specification by adding, editing, or removing required document structure elements, embedding fonts if possible and using other techniques. If such a conversion by direct modification is not possible, the PDF to PDF/A conversion engine falls back to secondary conversion options, which are Vectorization and Rasterization. Both these options perform rendering of the document content into a completely new document. Vectorization produces vector based graphic elements where applicable, for example, fonts and paths, and combines them with image resources while Rasterization renders the document content using the raster (pixel-based) approach.
The important note here is that both Vectorization and Rasterization approaches result in loss of fonts and text information because the text converts into shapes and raster images. Text information can be later recovered using OCR features.
Here is the basic workflow you need to follow. You can choose the PDF conformance level you require and the approach you favor.